As above many of the German companies private labeled, you would have to compare to loads of old German sockets to find a match.
Worth mentioning Black and Decker made a ridiculous number of drills and attachments for them here in the UK, was a standard issue item for the home DIY'er from the 50's on, largely because if you wanted something doing you had to do it yourself, most builders were fully occupied rebuilding from WW2.