Horseman
I am pretty certain BDL finish is not Imron, especially the early vintage ones. They are both polyurethane but several things about the manufacturing process make me believe it is a proprietary finish on Remington's part.

I also think I remember Imron as being a bit late for BDLs now that I think about it. I think Imron came out in the early '70s? My Google-fu is weak this morning.
art

Mark Begich, Joaquin Jackson, and Heller resistance... Three huge reasons to worry about the NRA.