When Boxockets were first introduced is unknown, best guess is 26-27. Attached is five different xs1618's, that would date from 26/27 to 1932. From top to bottom: First, model number is on back, width in center just smaller than 3/8. where the bar attaches to the socket the bar has a slight indention. No date code, no size stamps. Second, model number is on back, width just larger than 3/8. bar attachment is rounded. No date code. No size stamps. Third, model number is on front, width just smaller than 3/8. No date code. No size stamps. Fourth, model number on front, width just smaller an 3/8. date code -29. No size stamps. Fifth, sizes are shown on front, model number on front, width 7/16. date code on back, 1932. Has pat.no 1424069 on back.
I am not sure if these are in the correct order. If anyone has some more, please post a pic.
