I think this is possibly a 14HP Crossley radiator cap.The Dia. is 1-7/8". It has a 20TPI thread.The bakelite part is excellent, the base has a nick to one edge, but it should still screw onto a radiator.I can post this and I accept PayPal.
A nice original Lucas switch as fitted to Austin 7 etc. It appears to operate as it should and is in nice original condition. I accept PayPal and will post worldwide at cost.