The 1923 A model was the last of the original design,which began with#A506 although small changes were made throughout the late 1921 thru 1923 production (#A506 thru #A 7500).Some significant changes were made in 1924 (#7501 thru #20,000) and then again in 1925.Your #A4215 should have nickel plated steel drive shaft tube,steering rail,jtiller tube with leather “Bulldog” grip and steel warm air tube on carburetor as well as other distinctive features.From what I can see it looks like you have a nice complete example of an early “Waterbug.”
