Gens 1675-16750 case design compared with 1655 "1/1"

[Rolexaddict]

Gens 1675/16750 case design comparison with 1655 "1/1"

l told I will write something about the 1675 case design and thickeness as the 1655 1/1 is to fat and complete out.

Precision :

This is not a critic, or call it a constructive critic, as the 1655 case is an excellent case, it has a very good potential and will

stay for a long time the background reference to build a 1675 or 16750 rep.

Another precision for those who don't know the difference between a 1675 and a 16750 :

the 16750 is the modern version of the 1675. It has the new 3075 -28.800bph- movement with the quick date set and a different hand

stack by the way. Thats all. No way to ajust the GMT hand. This feature will come with the GMT Master II.

In the real world the Explorer 1655, the GMT Master 1675 and 16750 series use exactly the same case. These cases are very thin. 6542

GMT and early 1675 cases were still thinner !

Our rep 1655 1/1 has a thick case with a global design which is vrong for the purist but really interesting on another way, as its a

good platform to start many projects. For exemple, I would myself use this case to build a 16570 as it has the same thickness

I didn't take a caliper, I have 2 eyes, I observe the real stuff, then I copy. In fact i cannot find again my caliper, probably my wife took it and put in the garbage by mistake, thats life.

Lets see the photos

This is a 1655 rep case I am converting into a 1675 for a member. Right now I have just finished to enlarge the lug holes. That is

very common but will not make the watch.

Drilling lug holes and put a GMT bezel does't make the GMT 1675 trick. To build a 1675 which looks like a 1675 and not like a simple rep there is a lot of work to re-design the similar particular 1675 case lines.

The only problem which remains is the crown. On the 1655 rep case the inside space between the crown guards is more important than on the gen : The 5.3mm crown will look to small, so its easier to use the same 6mm crown from the Explorer 16570.

I am trying to find the way, probably by adding metal inside the crown guards. Thats another story.

This is a gen 16750 : observe the profile, the narrow space inside the crown guards, the small 5.3mm crown high positionned and the

bottom crown guards cut.

this is a another gen GMT case, a 16753 (TT) I have worked on, the crown has been removed to show the tube installation which is

machined very high

Now I am holding both the gen 16750 on top and the 1655 rep case. Look the difference. O.K, I told its the double of thickness ,I

admit I was to much categoric, sorry.

Now compare gen the crown guards bottom area

Here the rep 1655 crown guards bottom area

This is imho the most interesting view, the crown guards profile : on top the gen 16750, bottom the 1655 rep case

You see what I mean ? I think is complete off, no comments.

Another precision : my skin is very dry as I my fingers were in chemical and degreasers, I will put cream later

The other case side is pretty good

So the 1655 case has to be recut at several spots to get this slim design like gen 1655 and 1675 case. For this I recut both sides

and crown guard sides as showed here.

1 : Gaining a few 1/10 of mm inside the crown guards will allow the crown to be recessed, less protuberant. The trick is to don't let

the crown going under the bezel ring, it has to be at the limit.

2 and 3 : This cut will allow to show a more stretched crown guards profile

Here the red line figures the new break angle case side/crown guards side

To finish, a few thousands of material from the bottom of the case is also removed to get the slim thickness

For a comparison, this is a 1675 I have built for myself. On top the gen, bottom my rep. The profile is o.k, the crown is a gen 6mm.

A 5.3mm would look to small.

Again, just drilling lug holes and put a WSO bezel assy will not make a 1675, even with a gen insert, cristal, crown or what else...

TO BE UPDATED IN THE COMING DAYS

To show the work in progress on the 1655 rep case, this will be a very rare and particular 1675 for a member.

Edited April 17, 2012 by Rolexaddict

[woof*]

Thanks for posting this, very interesting

[the_rymeister]

Wow......... Simply amazing, thank you for taking the time to write this up

Amazing thread look forward to the updates

[danielv2000]

Agreed. Very informative.

[Guest zeleni kukuruz]

Thanks RA for taking the time to post this!

Like always very nice pics and where we can see what your talking about!

[lhooq]

Excellent post, JJ! Clear photos, smart observations, and good advice. I'm very interested in seeing how you narrow the inner crown guard gap.

[bigjule111]

Really nice thread. So accurately stated! The gen case is the way to go if u can find a cheap one.

[curlflash]

FAN!

[2Rol]

Yes, 1655 PC is a good start. But as RA said it is not so easy to obtain a very good looking 1675.

Very interesting and amazing work!

[bigjule111]

. First pict is josh 1:1 case u can see many differences. second pict is gen case with rep crown 3rd pict is gen case with correct gen 5.3 crown.

[Rolexaddict]

Thanks to all for your comments,

tomorrow complete photos of the work in progress and final result after repolishing

[tmg]

RA, great post, thanks for taking the time to put this together.

[dluddy]

Fantastic post. Even I understood the differences

look forward to part 2

[gplracer]

I cannot wait

[Ronin]

Excellent write up! So why is the 5.3 crown out? Is there too much space between the REP case lugs?

[Rolexaddict]

Excellent write up! So why is the 5.3 crown out? Is there too much space between the REP case lugs?

Yes, that it is,

Its easy to fix a tube and a 5.3mm crown, but the gap is not so important bur enough to disturb the general cosmetic profile

As soon i will have time I will try to reduce this space by adding little stainless steel shim inside and use repushing metal method, or I have also a special stainless steel soft solder paste which flows at 475°F, plus or less 250° Celcius very easy to work

pics of the work in progress and the final result in a few hours

[Rolexaddict]

All the case design modifications are made by hand in 3 steps : by filing with medium cut files, then machine pre-polished with high speed silicon wheels, then the finish.

The fist jobs for watchsmith apprentices is the hand filing. Get skills and hand precision to cut flat, square and make perfect angular cuts.

Good news : I have found back my caliper , usefull in fact to check regular tickness on a filed flat surface

Personally if have spend a lot of my holiday time in Florida with a master gunsmith, and I learn to file and file again... till the job came in my eyes and brain.

Many gunsmithes switched to watchsmithing, or opposite,

These little mods on the case would be possible with a milling machine, may be.

First cut is made to determine the new crown guards and side line using a round file. I use a very thin point permanent marker to trace the way,

The 2 first cuts are done on both sides.

Then the flat cuts

Now in red the metal which must be removed to give this particular crown guards bottom line

And, here we are,

WARNING : finger prints, some toolmarks are still there, its not finished,

After a few time of checking, pre-polishing, checking again.... The result before the ultimate and final check and polishing

Its not completely finished, I have to come back at some areas, achieve the complete polishing, then apply a light patina by hand, using #1200 wet and used sandpaper.

The gen 16750 and the case in progress (not yet finished)

The problem is still the 6mm crown, this will be the next challenge, adapt the 5.3mm crown

Edited April 19, 2012 by Rolexaddict

[the_rymeister]

Great work JJ these cases look amazing, you are truly a master at what you do

[Guest zeleni kukuruz]

Amazing skills and knowleg!!!

A few hundred emails back, JJ thought me the meening of the word "solutions" i have come to love that word after that! He is the solutions...

[correctime]

That's awesome.

Thanks for sharing.

[Rolexaddict]

Thanks to all for your interest

I will post another photo to show where are the mesurement key spots, in fact this case is very easy to mod, the CG side has more material than on the other side.

I am quite sure this case is a generic background used for many other watches, just a question of machining operations and case ref engravings

Great work JJ these cases look amazing, you are truly a master at what you do

Soon, same punishment for you mate, got the dial yesterday, he is good,

Edited April 20, 2012 by Rolexaddict

[the_rymeister]

Thanks to all for your interest

I will post another photo to show where are the mesurement key spots, in fact this case is very easy to mod, the <acronym title='Crown Guard'>CG</acronym> side has more material than on the other side.

I am quite sure this case is a generic background used for many other watches, just a question of machining operations and case ref engravings

Soon, same punishment for you mate, got the dial yesterday, he is good,

Brilliant news JJ I have the gen insert but still waiting on the watch but shouldn't be long.....now I've seen this thread I can't wait

[automatico]

I measured a 1675 (serial 555xxxx with 1575GMT hack):

case thickness at 3 o'clock measuring at outside edge with caliper pushed against inner bezel and caseback...4.6mm

thickness at 9 o'clock...4.3mm

at 6 and 12...4.35mm

overall thickness...12.8mm in center of crystal -- 13.35mm at magnifier

thickest part of lugs on outside edge of 3 o'clock side about half way between the crown and springbar holes...5.0mm +/- at both ends (hard to get an exact measurement)

on the other side...4.9mm +/- (hard to get an exact measurement)

caseback od...35.45mm

inner bezel (crystal bezel) od...36.03mm

between lugs...20.02mm both ends

Watch is in good condition, all genuine.

[Rolexaddict]

I measured a 1675 (serial 555xxxx with 1575GMT hack):

case thickness at 3 o'clock measuring at outside edge with caliper pushed against inner bezel and caseback...4.6mm

thickness at 9 o'clock...4.3mm

at 6 and 12...4.35mm

overall thickness...12.8mm in center of crystal -- 13.35mm at magnifier

thickest part of lugs on outside edge of 3 o'clock side about half way between the crown and springbar holes...5.0mm +/- at both ends (hard to get an exact measurement)

on the other side...4.9mm +/- (hard to get an exact measurement)

caseback od...35.45mm

inner bezel (crystal bezel) od...36.03mm

between lugs...20.02mm both ends

Watch is in good condition, all genuine.

Pics ? blue prints ? it would help

Anyway, with or without mesures, Chinese reps Rolex cases are usually to thick and out of specs,

This is a gen

Gen 16750 profile :

For me, the most important spots to sculpt a 1655 rep case to convert it in a "looks like" gen 1675/16750 copy :

1 - the thickness at this spot, which is VERY THIN for gens,

2 - the crown diameter, this is easy and an evidence, here its a gen 5.3mm, we are vrong with reps,

3 - very important cut angle of the bottom crown guards area

4 - the curve of the top and bottom case end profile

A palmer (micrometer) instrument is better than a caliper, but, the goal is to get a "looks like"

imho, a list of 1/100 of millimeters mesurements is not the best way to work,

skills and CREATIVITY are more important than rigidity of basic secondary education

[Star69]

my 2 €z :

1 : its not the thickness - this case part is just polished different than the rep case - a little polishing by hand makes the rep case lock exactly like the gen - not only on 1675 - on all vintage Rolex reps.

2 : not fixable - only if you pull some stunts - which is not worth is esp if you are keeping the cheapo Asian movement

3 : same for all vintage Rolex reps CG shape on top and button are different - some modders use just a Dremel with a cutting wheel = case ruined

4: this curve is changed by Rolex over the year all the time - alone the 16610 has at least two case that are completely different in this area

all in all why so much trouble ?

we all know with a little tweaking the Josh case will look nice - but never really fool anyone - the old Noob GMT II middle case was way better or the TC 16610 is also way better - maybe someday the make some

new vintage cases ....

cheers,

Frank