Mapman: early 703s look like 702s. Easiest way to tell the difference is to place the crown coronet-side down.
On the 702, the threads run all the way to the top.
http://www.chrono-shop.net/img/p/953-5005-thickbox.jpg
On the 703, they don't.
http://img.auctiva.com/imgdata/1/4/9/0/1/4/9/webimg/572089904_o.jpg
Looking at the tubes, when installed the 7020 has threads near the case, but is then smooth:
http://www.chrono-shop.net/img/p/3042-22122-thickbox.jpg
For the 7030, the tube has a smooth spot near the case to fit a gasket, and then is threaded:
http://www.jewelerssupplies.com/media/R7030.jpg