The Hollenbeck and Three Barrel Gun Co. drillings that I have seen had the rifle caliber marked on the barrel flats like this Three Barrel Gun Co. , serial 570


[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]

Last edited by Daryl Hallquist; 01/08/24 11:48 AM.