I've looked through all my front hubs and found two that have the speedometer gear shoulder. One has the shoulder and the three screw holes and is 5¼" long. My reading of John Regan's article in the encyclopedia puts that between 3-14-17 and 6-25-18. The other hub has the gear shoulder, but not the screw holes. It's 5½" long. I assume it's a later version, but I don't see anything about it in the encyclopedia. The first Rodda volume mentions both hubs but doesn't go into detailed measurements and dates. Can anybody here pin down a time period for that second hub?