Chip may be right. That is definitely a 2-pole breaker, looking at the difference between the two halves' labeling. I believe that to be either a Bryant or T&B breaker.

I was thinking that this is one of the neatest older panel installations I've seen. What catches my eye is the poor cable-clamp installation on the 10-3; the newest part. [Linked Image]

Larry Fine
Fine Electric Co.
fineelectricco.com