I was just given this 1940-1960s(?) alidade
which bears a factory stamp "U.S.G.S. 198".
It seems to be the classic Gurley 584C model extensively used
by them. After inspection, cleanup, and some lubrication, all
is in order, except for the missing eyepiece. It also needs new
platinum wires for cross and stadia lines
- or a spider willing to cooperate.
Below are photos of the instrument. The blade is 18x3 inches,
with striding level, and `Beaman Stadia Arc No. 330' with solid
silver scales.
The eyepiece mount measures .700" outside, .615" inside diam.
There seems to be some allowance for the inside diameter.
Need help locating a suitable eyepiece.
