The rear miter box input sprocket is a hot mess. It was drilled at least 3 times for 3/16″ and 1/4″ diameter split pins. It is a Browning 4016 x 3/4″ keyed sprocket. 40 means #40 teeth and 16 means a 16 tooth count. 3/4″ is the bore size. Any other bike this would be in my scrap steel bucket but I will run it because it was working just fine during my first rides. 16 teeth means this bike is very fast for a 2 stroke Albion bike. 25 MPH maybe more.
The picture below shows a 3/16″ drill bit at 1:30 that was drilled through the 5/16-18 UNC threaded hole at enough of an angle to break through the face of the sprocket. There is a 1/4″ drill bit at 4:30 and a 1/4″ split pin at 10:30. The 4:30 hole is tight on the pin but the 10:30 hole was drilled way oversize and does not line up very well with the 4:30 hole. The miter box only has one slightly off center 1/4″ diameter hole. The 1/4″ pin only goes one way. I will use the 1/4″ pin with 2 or 3 loops of safety wire through it and a 5/16-18 UNC set screw shown at 1:30. The miter shaft is not keyed.