Since Service Aces are physically the same as other target-sighted O-frames, why will your case hold only Service Aces and Aces (which are shorter in the slide than Service Aces) to exclude Government Models, etc.?
On the later colt service ace 1978 the rear sight is right at the end of the slide,early guns were about half inch foward. Who ever made this case made it to fit the early aces,, the inserts were cut to clear the early sights.
I assumed your reference to "early guns" meant Pre-War, and I was skeptical about your statement that the case would hold only Service Ace and Ace pistols, since the Service Ace and National Match and Super Match use the Stevens rear sight, which is far different in location (to the rear) and much longer than an Ace, which has a rear sight about .25-inch in length placed ahead of the rear of the slide, much as you describe.
I wondered if you might be referring to a difference in the rear sights, but I did not understand how that could be the issue because Service Ace (and other pistols using the Stevens rear sight) and Ace rear sights are far different. If the box is closely fitted to the Ace rear sight, it will not fit the Service Ace or National Match with the Stevens rear sight. If the box is closely fitted to a gun with a Stevens rear sight, it probably will not fit an Ace.
Which style of rear sight will the box accept, the Stevens or the Ace factory rear sight?