Well a fiver in my case
My father in law ( also Bill ) worked in the later part of his life for LS Starrett, an American firm who had a factory in Jedburgh where he lived, they made machine tools and measuring equipment, sadly closed down in that part of the world around the early eighties.
So my eye was caught by an item on Ebay, a micrometer made by Starrett for BSA.
I got it for 99 pence plus £4 postage, it's a long time since our science teacher Mr Williams showed us how to use a micrometer but I'm sure I'll work it out or ask at our local machine shop (pride goes out the window with age and a quest for knowledge).
Possible it's not accurate, although it does sort of agree with my vernier. I don't know if you can reset them or get them reset, haven't got that far yet, in any case it might be fine for comparison work.
But best of all it has magic words on it BSA and Starrett, possibly of little importance to anyone but me