They're not impossible to find, the cases dials and movement turn up on eBay quite a few times every year and a NOS rather than original won't be worth as much as an original watch, the $3k offer sounds reasonable if you're going to sell it.

 

Just as an example you've got these on eBay right now:

http://www.ebay.com/itm/NOS-Omega-C...113557?hash=item2a4a88eb55:g:ozEAAOSwm8VUtFSoPurchases made through these links may earn this site a commission from the eBay Partner Network

http://www.ebay.com/itm/OMEGA-DE-VI...058251?hash=item58d1dd390b:g:UJcAAOSwwE5WWNFwPurchases made through these links may earn this site a commission from the eBay Partner Network