1940s Holdsworth (probably), but no idea what model, and it's £25 so far.
Also covered in black sh*t.
https://www.ebay.co.uk/itm/355675983010
From https://www.nkilgariff.com/Models.htm
Pre WW2 all Holdsworths had clip type headsets except L'Internationale. This model was new for 1939 and had...