Hio, Folks.... These things went away from the market decades back. I used my last one, and was hoping some old-time builder might still have a couple in the drawer.
For the benefit of the latest and greatest crop of rod putter-togetherers: A bogus butt box is an anodized piece of aluminum, open on both ends, and ~swaged~ one end to take, trap, and hold a rubber mushroom end cap. Remember those old wooden handles on boat rods, with the mushroom? Same idea, but with a bit of aluminum to take the shroom.
The aluminum is bonded to the rod, the mushroom cap popped on the end, and Bob's your aunt's live in lover. If the rubber gets torn or worn, you just replace it, instead of the entire butt box. The common colours were burgandy and black, but they came in other shades as well. Cheers, Hope a reader can assist now that I posted an image below. Thanks, KD.