I belive you are talking about the " heater box " tin (common name).
There are 3 pieces.  1 piece goes on the # 3 &4 side and 2 pieces on the #1 & 2 side. They mount to the heater box tabs and to the side of the case. When you find them,make sure they are for a 15-1600 type-1. I don't have any extra at the moment but they shouldn't be to hard to find.

Well I removed them and they are a bit rusted thru in a coulpe of places, should I try and find some more ? I been lookin cant find any...dang.....Fred