I too have an old H&R top-break revolver that I am trying to research. From the other responses in this thread (thank you!), I found the serial number under the top of the frame and under the left grip: 1565. There is no caliber marking on the gun anywhere, but it looks like a .32, even though it is a six-shot. Another thread on H&R top-break revolvers indicated that they came in 7 shot .22 and 5 shot .32 models.
Aside from the serial number, the only other writing I can see is the number 565 on the back of the cylinder and on the cartridge extractor and the manufacture info on top of the barrel. That info is: "HARRINGTON & RICHARDSON ARMS COMPANY" (top line) and "WORCESTER MASS. U.S.A. PAT'D OCT. 4TH 1887." (bottom line).
I would like to find out the year of manufacture, if it is indeed a .32 and if so, if it can fire modern smokeless .32 S&W rounds.
Thanks in advance!
Here's some photos:
H&R Revolver - Google Photos