That is Stuart.
The single eye is the giveaway.
nahh it was bicBiro: László József Bíró or Ladislao José Biro was a Hungarian-Argentine inventor who patented the first commercially successful modern ballpoint pen.
My guess is it’s a slip gauge holder, does it have a little longitudinal screw to clamp slip blocks together beneath the thumb screw on top?
edit yes, I’ve clicked the photo to enlarge and I’d put good money on it being a holder for slips