It might have been made under the Iver Johnson patents for their "hammer the hammer" safety mechanism. When the trigger is pulled to the rear, a bar comes up between the hammer and the firing pin, so that the hammer's blow is transmitted through the firing pin to the cartridge's primer. Look inside the hammer's slot, to see if this happens.
Its probable caliber is either .32 Short or .38 S&W. Measure the bore (not the cylinder's chambers) to see. A .32 would measure about 0.30", and a .38 would be a little bigger than 0.35".
Iver Johnson made pistols for lots of different wholesale and retail businesses, each lot with its own private trademark, so the guns weren't always marked "Iver Johnson."
It's possible, but not likely, that your pistol is a Harrington & Richardson. The trigger is the wrong shape.
It's also possible, but much less likely, that your gun is a Spanish-made copy of the Iver Johnson design.