1931 running boards

My 1931 Express u124 running boards are wood with a steel cover. They are being glued up now as we speak. Question I have is were these painted or left natural? The covers were painted black.

The wooden floorboards in the autos were coated with some sort of petroleum based preservative, ( I may be mistaken on the petroleum part ) I believe this led to a darkening of the wood, other than that no paint, I would think the runningboards would be treated in the same fashion but just a guess.

I wonder if it would have been linseed oil.

I talked about this with someone in the past but cannot remember the specific details.

Either way it only makes sense that there would have been a wood preservative of some type and I am positive paint was not used on floorboards.

I cannot say for your runninboards though.