Of all of the Bumer Fillers I have pulled from M38s over the years, I'd have to say they were raw wood. I just finished mine in my restored M38 with boiled Linseed oil to preserve it.
I've made & sold tBumper Fillers in the past (along with other wood parts) and will be making more for the National show in Huntsville.
I want to live life, til the day I die.
One Big Ass Mistake America