Hi Dash look regulary doing eBay.de , mine popped out there form Stuttgart was NOS of course for 900€ , this as some days before you .
Long shot, but maybe the buyer of this lot only wanted the links, so why not ask the auction house if they will tell the buyer of you're interested in the caseback..... 'speedmaster' | Lot (3) Rolex & Omega wristwatch parts | Jones and Horan Auction Team (hibid.com)