I didn't see that one (#2693).
D16517 is S/N 2793 and listed for $5,750
They say it has good rifling and some oxidation (whew, glad it wasn't rusted).
It has a grip strap marking "WD 579" which they say is Danzig Dockyard.
It looks nice, but no mention of matching parts internally.
You should ask.
I would expect they are, though.
Simpson's has a stellar reputation and an impressive inventory.
They are on my Bucket list for a personal visit one day.