Marlin Ballard caliber search

[Pkgunsmithing]

Customer has brought in a Marln Ballard, s/n 29074, but with no caliber markings. Obviously looking for the caliber and approximate value.

[marlinman93]

Almost all Ballard rifles had no caliber markings until the 1880's. So impossible for anyone to look at the gun and tell you what cartridge it's chambered for. Only true way to discern this is to do a chamber cast with Cerrosafe. Then the casting can be measured to determine what it's chambered in.
Your image doesn't work, so not sure what it is showing? But if you post the rollstamp info on the left side of the receiver, and how many lines it is formatted in, with approximate bore diameter read with dial calipers, I might take an educated guess what it "could be".