Re: Question about Hopkins & Allen Arms Co. revolver
Your revolver is almost certainly chambered for 32 S&W, judging from the size of the cylinder compared to the trigger guard. The guns made for that cartridge were cheaper than the larger ones made for 38 S&W, so more of them seem to have been sold and survived to the present day.
32 S&W is a weak round, but the modern smokeless powder version of it develops higher peak pressure than the black powder version these guns were often made for, so you are correct, firing it is not a good idea.
Full retail for your gun was about $4 or $5 back in 1910 or thereabouts, and when Sears sold H&A pistols by mail order, it was even less.
This type of gun is more or less a copy of a Smith & Wesson design dating back to the mid-1870s, and produced in large numbers by a variety of companies until about 1930. Production of this general style did not end completely until WWII, but H&A was bought out by Marlin-Rockwell (as it then was) in 1917 and ceased production. HTH!