Speaking of stale calibers, or more specifically, stale ammo sizes, what about 38 S&W ammo?
https://www.forgottenweapons.com/38-sw-the-other-38/
Linked article says, "Other names for the cartridge exist like “.38 Colt New Police”, “.380 Rim”, and “.380-200” depending on the market and manufacturer."
The reason I post this here is twofold.
1. Try searching this site for 38 S&W and you will get S&W 38 Special pistols, not 38 S&W ammo.
2. I could have had a revolver that shoots this outdated ammo. Today I ran across a receipt from my dad purchasing a revolver in 1968. It says
1 H&R Defender
Cal. 38 S&W
Model 925
Serial# AE26127
Total with tax, $51.95
Paid in full. Hold for permit.
When dad passed in the 1990s we found a couple pistols, an H&R that was smaller than this gun and looked chambered for .22 and a tiny Astra .22 short pistol. But this H&R Defender I never found. He must have parted with it at some point. Alas, the things we fail to keep that later we wish we had.
Now I remember an old gun permit that was issued to him and just looked at it and it has the same serial number.
Here I just found an online image at an auction site. So it is a top break. I was 10 years old when he bought this gun.