I think there's a simple question that will help sort this out for me.
Is the black finish on the black peghead and black front of the mando highly polished and shiny - looking like shiny thin laquer coat. Also is there a laquer coat over the gibson logo on the peghead. My gut feeling is they were nitro coated.
Once again thanks Ned. I heard from Dan from the mandolin archive, he tells me some blackfaces of this period (serial numbers) were nitro coated on the face and peg head. This would tie in with the very shiny finish you have and with the very shiny finish on my peghead. So I've decided to go with Nitro for the front and peghead.
I've patch repaired the finish on the back and to blend it in, overcoated with blonde French polish so the original finish is still visable.
Hopefully I've got the balance right between renovating and preserving oringinality.
Thanks so much for your help. Instrument repair is a constant learning process.