Difficult to measure with absolute accuracy unless...

by Hoot , Diversityville, Liberal-sota, Wednesday, June 12, 2013, 13:15 (4186 days ago) @ cable

it's "over pins" (Option 2 below).

Two thoughts...
An inside caliper 'might' get you close enough. This assumes there aren't that many choices and that the choices are further apart than a few thousandths. The edges of the caliper won't get into the corners far enough so the slot will be a skosh wider than the measurement.

If you had a couple of pieces of smooth wire, you could put them into the corners of the dovetail, measure between the wires as accurately as possible, measure the wire diameter, report it and then I'll dust off a couple of long unused brain cells to give you the calculated dovetail width. Gauge pins are best but any smooth, straight, consistant wire should do. We'll have to assume the dovetail angle on this one but I'd bet pretty heavily it's 60 deg.