I’d be curious to see the end-to-end dimension of the tool in #5732 .. This
generically seems to be a go / no-go tester for thickness of sheet metal or
anything else being made with a critical thickness dimension in either flat or
curved material being measured.  One end would be held on a reference thickness
(gauge) and the other side of the tool would be slid onto the edge of the item
being tested — if it clears the edge and slides across, then the thickness is
less than or possibly equal to the comparative gauge thickness.  Whether that is
good or bad depends on what is desired.  No doubt at all that this style tool
could also be used in the watchmaking trade as well, as parts that are made
either too thick or not thick enough could cause an issue with watch mechanism
clearances or accuracy (by varying the momentum of the spinning part/mechanism);
measuring of curved parts would be aided by having the round button tips Kirk
mentions.

#5736 initially looked to me as the micrometer core of an inside micrometer, but
whether that is true or not would depend on how the reference shoe/foot was
attached and referenced to the surface to accurately measure depth.

Charlie Driggs