https://www.ebay.co.uk/itm/Runbaken-Vin ... 3908908885
it was listed at £50, now they've dropped it to £40 +p&p
For anyone reading this once the ebay page is lost in the future, here's the image, it's a battery charger that plugs into a light socket.

I recon it's early 50s, before the rollout of the modern wiring standards.
Look closely and you'll see it could still take the light bulb below it, it's basically a through connector with presumably a tiny transformer/rectifier built in


The company seem to have been around from the 30s to the late 50s, perhaps some older members here remember them.
https://www.gracesguide.co.uk/Runbaken_Products