Wow!! That could be a worthy restoration project. Any pictures of the 2 7/8 markings? According to surviving hang-tags I've seen, Remington Arms Co. 12-gauge doubles were made for 2 5/8 inch shells. In his book, the late Charles Semmer showed a CEO-grade with 2 3/4 markings on the bottom of the tubes just forward of the barrel flats.
I'm sure that with a liberal application of dollars one of our good stock men could make it look a bit more like this --
