Twolite flat glass lens, 4 1/8 x 3 37/64. Made by Mckee glass co. I dont have any idea where this is used. But someone would know. Maybe a motorcycle. Has patent 1604935 on lens.its in excellent condiion. I see a very light curved scratch about 3/4" long. Its hard to see.No stone chips, no sand pitting, its been in my tool box 40 yrs min. I cant find one this size on the internet. Lots of other sizes. Ck photos.