Sam,
Thank you for your reply. I never heard of these either until I acquired it and started doing some research. These were made back in the early 1900's up until about 1945. They are small single-shot .22 and chambered for shorts and longs (not LR). Here is a website that provides some background on them:
Hamilton Rifles
I have attached some pictures as well. I'm trying to search the web for a replacement rear sight but not having any luck. Thanks again for your reply.