One thing I will say, thinking on my answer about what is a "pocket pistol." Not an expert here. But, one thing I just recalled is more people back in the day carried a pocket pistol without a pocket holster, if I'm not mistaken. One thing I've noticed is that all of these guns are even more concealable without a holster, including the marginally too large subcompacts (shields) or revolvers.
A holster does add some bulk, thickness, slight lengthening, etc.
So those old school pistols that were considered pocket pistols but were larger than our LCPs/Tomcats, may have been carried without holsters right?