Hi recently I was given an antique optometer and it is unmarked so I was having trouble finding who made it and when. We narrowed it down to the 1920's-40's tentatively, and someone told me to check the lightbulb to see if it could be original to the piece. It is a blue Mazda bulb stamped with the GE logo. It also has Made in the USA on the metal. Could anyone give me some information on these bulbs. Thank You
