This bolt had 307A-L , Victor. Each bolt seemed to alternate between Lewis and Victor. Not sure of the significance of why they alternated, but a google search shows they could have been the companies who manufactured the bolts.

Lewis probably refers to the Lewis bolt and nut company.... https://www.lewisbolt.com/
Victor Specialties - sells assembled nuts and bolts.
https://www.victorsp.com/product-catego ... uts-bolts/