Thanks for the comments Joe. You motivated me to look at the Smith Lenses that I have and here is what I noticed:
Several are about 7 13/16 overall diameter with a 7 inch prism (rim opening size). None of these have sizes cast in the lenses so perhaps they were marketed as 7 ¾ size but the overall diameters on mine all measure slightly larger and all are the same size. I expect these may be the size for early Chevs as one of them had a hand written tag saying it was for a 1923 Chev. I have three lens combinations in this size:
1) Four locating notches with no patterns in the upper and lower sections of the prism face
2) Four locating notches with rectangular patterns in the upper and lower sections of the prism face
3) Two (lower) locating notches with no patterns in the upper and lower sections of the prism face
Please see the link with pictures to illustrate.
https://www.dropbox.com/sh/kt1o8sdt6focpyq/AAA2JfFpMdzF4Y0U1wQfnp19a?dl=0Hope this helps the discussion.
Can anyone confirm if any of these are correct for early Chevrolet vehicles? and if so for which applications.
By the way - I also have some larger Smith lenses (last photo in the Dropbox folder) with no locating notches in the flanges and with sizes cast in the top of the flanges (above the prism so not visible when mounted). The sizes I have are 8 3/8, 8 ½ and 8 5/8 and these match the overall diameter of the lenses. I believe these are aftermarket replacements rather than original Chevrolet lenses and the sizes are marked to assist in selection. The prism sizes for these are 1 inch less in diameter than the overall diameter in each case.
Tom