.25-36 Marlin cartridge, by Peters, U-marked primer

I have a Peters headstamped .25-36 Marlin cartridge with a small primer marked “U” and a correct soft nose 117 gr. bullet with crimping cannelure for the Marlin case. The round does not look like a reload, but I can’t see why Peters would have used a U-marked primer. Is this a factory round by Peters, or just a careful reload? Jack

Possibly made after Remington bought Peters in 1934.

Guy: Your answer seems plausible, but had I checked over the round more closely I would have noticed two small oil dents in the neck just above the shoulder. It’s a handload, and a careful one. The bullet looks early, with either a cupro nickel or tinned gm jacket. Jack