What is the complete serial number on the gun frame? With all the serial number duplication from different production periods, how can you/we be sure you have a 20's vintage gun without a serial number? On pre-13 guns one will see a variety of barrel stamps, and barels not stamped; but stamps are usually very consistent as to Grade and manufacturer ID on post-13 guns from the Crown Grade downwards. Without seeing the gun, yes; the stamp may have been omitted, or perhaps the barrels have been factory replaced after the Marlin acquisition, or perhaps you have a Marlin era gun and have mistakenly ID'd their "S" serial number prefix as a Specialty grade stamp mark? But even if the Hunter Arms Fulton, NY roll-stamp die was broken on the day the barrels for your gun were produced, it is doubtful that such an omission would increase the collector's appeal of the gun.