He had a very interesting box of .38-55 UMC bullets that were "254 grain" marked on the box! Never seen any in this oddball weight? He also had a box of JM Marlin marked .38-55 255 gr., but I have the same box in nicer shape. Then I spotted two boxes that caught my eye! Both .40 caliber, paper patched, with one being 285 gr. and the other 330 gr.! So we worked a deal and I brought both home.
These would have been for either Marlin Ballard single shots in a few different cartridge chamberings, like .40-63B, .40-85B, or .40-65B chamberings, or even the 1881 lever action model in .40-60M cartridge. I always look for Marlin marked ammo, or bullets, but rarely see any in recent years. Didn't see a lot decades ago either, but they've really dried up now.
Of course these wont ever be loaded up!
These were likely made for Marlin by UMC, as the two companies often worked together on cartridge development. They will date to 1881 or newer being marked "Marlin Firearms Co." I have some older boxes of bullets, and ammunition marked "JM Marlin, which would be pre 1881.