Museum Quality, Spencer HB-Meter.

This is Very Cool Pocket size Hemoglobin Tester, Made by American Optical Company Instrument Division. Buffalo, New York Made in USA.
(Serial No. 22315) Inside Lamp: Mazda #233 (Purple Bead) 2.3 Volts 0.27 Amp G 31/2 bulb, Battery: Size '' C '' Flashlight. Scale on one side, Grams Hb per 100 ml and blood chamber clip. It is very Cool backlite, When you look through eyepiece and press little button, for reading samples.
I dont know about the Age. But there is one piece in British Columbia Medical Association Medical Museum. Shows Manufactured from 1950-1975. If anyone know more and about the value helpful, Thanks for Looking.