They were certainly supplied with posh cars in the 1950s...but that doesn't help much.
The standard magneto spanner and feeler wouldn't be much use on a coil ignition vehicle so presumably they could date back to when Lucas first made distributors.
I found a complete pre war MG toolset in one of the pre war MG specialists' stalls yesterday, and that one contained a magneto screwdriver as shown in your picture. So if that MG specialist knows his stuff, this must be a pre war tool...