^ I am going to guess prior to the Ingersoll-Rand acquisistion, when it was still part of the Penens group.
The graphic with the Corinthian helmet was used as early as 1951 and as late as 1965 from the scant documentation I have, but it may have been used prior or later - that's all I have documentation for.
Inexplicably, neither their 1963 or 1978 catalog show any display boards.
I do not believe I own any 1/2" drive Challenger, although I do have complete 1/4" and 3/8" drive sets.
correction:
After looking at these graphics more closely, I noticed that the part numbers on the sockets were changed at some point, so your board cannot be as early as 1951. I do not know when the change in their part numbering system took place, but the 1963 catalog shows the same part numbers as those silkscreened on your board.