Axel Peterson was the younger partner in Schoyen & Peterson in Denver. He made both center fire and rim fire barrels, and his good ones are as good as they get. Unfortunately, toward the end of his barrel making days (approaching WW2 era), they are not all good.
The offset bore is, as you surmised, to allow use of the center fire firing pin. Many of their Ballards have a tapered cross pin installed in the action to permit "take down" without a barrel vise. Whether this was for multi-caliber sets or just to facilitate transport on trains is open to debate.
