Lagopus,
Slight correction:
The mark for chambers not less than 3" would be "LC", not CL (I was very pleasantly surprised to find the LC mark on a recent purchase...); was the service charge weight for the LC/3" really a whopping 1 1/2oz?!
Sorry, thread drift...

Nice old gun; great to have a family provenance, and great to have access to such detailed information on the individual gun's "birth". (there, I'm back on!)
RG