A friend of mine likes to buy old tools and smilar at car boots, and he picked up a set of bits which neither he nor his friends could identify. He showed me two of them:
They have two tips, one mounted radially outboard of the centre tip but pointing parallel to it, offset by a gap. The gap varies through the set and the bits are numbered, I am guessing they correspond to the gap/offset distance.
Reverse side:
They look like they have (tapered) square shanks round shanks, but I will double check that with the chap who bought them.
If I was forced to guess, it looks like they are intended for scribing or cutting a circle? My non-exhaustive research didn't show up anything identical; the closest with two tips I could find was the adjustable bit on a DIY FAQ.
Update from the guy who bought them: "They have round shanks and are numbered from 10 to 64 all in a fitted box with the brass hand drill. They are made of steel which appears to be quite brittle as I broke one when I was trying to remove it from the box."
10
and60
markings correlate to any known units of measure?