vintovka, I think
https://www.stovebolt.com/ubbthreads...ml#Post1157527 this will help.
If not a member you should check out the other site. Lots of very knowledgeable old guys hang out there (hopefully this won't get me banned, we stovebolters need all the help we can get).
My experience was you have to use a original black steel mirror arm since it'll require a bit of heating and tweeking (not much) to work with the 5x7 mirrors. You'll see what I mean. I tried to cold bend a new chrome arm and it broke... pot metal. I suspect all after market ones even if black are pot metal.
Good Luck, RonR