1942 to 1947
No. 20 is an elbow calker
Check the weight, the tools were 5oz each, so I woud guess it would weigh between 3.75 lbs to 4 lbs.
Yours may be different from the 1/2" calker. How long is the box?
The February 15th, 1942 pricelist shiws a list pruce of $1.00 each, and a net price of $0.55 each.
Pics coming
Chilly