Other than color, you could be forgiven for believing these two pieces of beadboard are the same. I would be a hypocrite to fault someone for the same sin I committed.
The darker piece of wood is the original soffit beadboard. The lighter piece is a sample piece I picked up at a local millwork store. I called them several months ago and asked them if they had beadbeard. "Oh yes. We have traditional yellow pine bead board. It's three and a half inches wide and $0.85 a linear foot."
Knowing that I had sourced the beadboard, I tore into the soffit on the south side of the house, scraping away loose paint and removing rotten beadboard, until things looked like this.
When I went to get the new beadboard at the millwork store, I took the darker piece with me, just to be sure they matched. I found out what I should have known all along. Today's beadboard is 1/8" of thinner and an 1/8" narrower than beadboard from 1921.
I could get around the thinner bit by using shims, but the reduced width is a real problem, especially as row after row of beadboard is placed next to the original. First I'm off by an 1/8", then a 1/4", then 3/8", etc.
My options here are neither great nor cheap, but what I'm leaning towards is getting this, which would allow me to create my own beadboard.
Suddenly my quick project of scraping, repairing and painting the soffit is looking like it could take all summer.