Congrats! That's a pretty good case. Looks like someone's been a little enthusiastic with the chamfers, but nothing too much to worry about.
Case back markings look to be good quality, the serial number is unusual though. It should start with 0552 (Royal Navy) or W10 (British Army) rather than 6645. I was intrigued and just googled it. This 5517 has your serial number! As you'll see in the shot of the case back, the serial starts with W10/6645...:
http://www.thetimetraveler.co/watches/sold/198/5517/5517-full-spec-all-original-milsub-w10/
As you're in the US, Phong is probably your best bet in terms of service and shipping – he's based in Arizona.
There are a couple of semi-reliable high-end suppliers from Vietnam. Minh Quy (MQ) is one you may hear about. He's tricky to deal with. I personally won't be dealing with him again after receiving a shoddy case and poor service. Others have had a better experience with him though and his dials do look good:
http://vintagewatchesmq.com/minhquy/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=800&category_id=146&option=com_virtuemart&Itemid=1
Ruby is another, however she's not always responsive to messages via the website:
http://rubyswatch.com/Products/h1-1-|-vintage-|-submariner-|-military-|-5517-|-dial-2106
Looking forward to seeing your build come together!