Antique Ophthalmic Instrument

Description

Antique Opthomology Instrument
Marked:  Giroux, Paris,
Marked:   CONVEXE at top and bottom on both sides
It has 10 different pieces (various strengths) of glass, loose, stacked in the holder. numbered 1 through 10, held in place with 2 screws, 1 on each side at the top.  I do not know the type of metal of the holder.
The  rectangular glasses are 3/4 x 1 inch and the tool is 12 inches long, 3/8 inch wide and weighs 3 1/2 ounces.
Used by a family practice physician (my Dad), Watertown, MA, 1930's.