Hello. I need the year of manufacture of a U.S. Revolver (Iver Johnson) Hammerless .32 caliber 5-shot top break revolver, 3 1/4-inch barrel so I think Medium Frame since it fires .32, not .22. The serial number underneath the barrel is 55931. There is no stamped information under the handle. The handle grips are hard rubber with the "U.S" logo up top. My guess is about the 1920s? Thanks so much.