Came home today with a well-patinated Cornwell extension bar in 3/8". It's 11 1/2" long.
Marked on the top end: 13 CORNWELL 3
The date codes are a little cryptic, but AA seems to suggest that mine is between 1934 and the late 30's.
Don't remember seeing any old tools from that brand before, but glad to see that they are still alive and well.