Thank you for mentioning that - some very nice, American factory made firearms DO NOT HAVE SERIAL NUMBERS! My nephew had a beautiful Savage Model 311 12 gauge double (inherited from his dad), with color case hardened frame, walnut furniture, and 28" or 30" barrels, that was manufactured and sold without a serial number. There are probably thousands of similar firearms in LA...
Mines a 16 gauge Harrington and Richardson double barrel.
Don’t even know when it was made.