I am going to guess that that case back is a replacement as it has no sn, my non ord marked back has a sn on it, and it is likely that all factory with the watch case backs did. A replacement from an outside source or even from Bulova would not likely be numbered. Now this is just my thoughts on it, no proof or evidence but makes sense to me. Are you going to replate the case? I am considering it on mine.
Apparently there were unstamped watches issued for use before TM 9-1575. I plan to leave the blank back case as is. Negative on the plating also, the brass is smooth with not much pitting.
"Apparently there were unstamped watches issued for use before TM 9-1575."
Wayne,
Where do We find this information?

According to the information above identification marks would be added at time of service to Military Watches manufactured prior to 12 November 1940 - which indicates all issued Watches manufactured post Nov 12, 1940 will be stamped accordingly.
Fifth
Yes they were supposed to be stamped. What would you like to do about all the watches that exist without stamps? I cannot find the stamping requirements & will delete the info from the description until I run into the source document.
These were made and issued for several years without a stamped back and as they were a disposable item, ie not turned back in, I am sure many were pilfered for personal use and reported as lost or just never turned in and thus never stamped.
In reply to These were made and issued by shooter144
I give it 3 stars
sure were a wide variety of stampings on these various military case backs. Good arguments for all examples. I gotta dig out and re-read my military timepieces handout that was associated w/ the 2001 NAWCC military watch collection/special exhibit. I knows I gots it somewheres....
Again, I gott go read up. The source document indicating all post 1940 watches were stamped when issued would help me assign ticks when published as a Military Issue". Two ticks for now....as the "Issue" is the issue.
With Jerin's ad, which I did not know existed, these could be either Re-issued or un-issued, no real way of telling, although there are others without ORD markings that have numbers stamped on the case back, but this one appears to be bare.
I saw examples both with and without "case SN's" stamped on the back (w/o ORD markings). Those with "numbers" perhaps original to the case, those without possibly replacement case backs? May not address Issued, vs Non-Issued though. Jerin's ad helps muddy the waters at first, but then things clear up as I re-read it too. Great ad!! Great off-site resources for this stuff....just takes time to read up- then I gotta also understand what I'm reading- which is turning out to be more challanging than the simple "reading" part.