What age is your Iron Horse? A question we get asked a lot and have struggled to find a definitive answer to. The following guide will help give you at least a year of manufacture.To attempt an illustration we have used an actual Iron Horse engine number...and here's what those numbers mean...Deciphering your Horse engine number centres on the second digit. This is your year of manufacture and the letters run in twenty year cycles, remembering that JAP years actually start in the September of the previous year. In the example above the year is 1948 but theoreticallyit could have been made in September 1947 but not after September 1948.The first digit is the model number, in this case the Horse used the Mk 5 engine and is so denoted here. Then comes the year, then theengine number (which we have no details of, it is just a factory record), and lastly the modifications. These are what the factory calleddeviations from the standard specifications and could denote cam spec, piston type etc. We have the codes for motorbikes butunfortunately the Horse engines were designated as industrial motors and the codes we have don't apply.Please see the next page for the table of what the numbers mean.