Pictured below are my 1913 edition of the 1908 Colt Vest Pocket .25 ACP (the original Mousegun?) and a modern-day .380 ACP pocket pistol that is 96 years its junior. I consider the Colt both a mousegun and a viable defensive option with 50 gr. FMJ cartridges, although I carry the LCP on a regular basis. The Colt is fun and easy to shoot, and is quite accurate at SD distances. As you can see, the Colt is
quite a bit smaller than the LCP, which I do not consider a mousegun but just a super-compact gun shooting a mainstream cartridge. Fully loaded (both 6+1), the all-steel Colt outweighs the Ruger by only 2 ounces (14 vs. 12) and out-
classics it by a mile.
Added - Except for the grip, the Colt is thinner than the LCP by what appears to be 0.1" or so. I'll try to put some calipers on it to be a bit more precise.