Before 28 the factory had an array of names for their different models. Especially Scout where called different names for their versions. And the ACE 4 was in for a lot of changes.

A new line of bikes where planned for -28 forward and they decided for a more consistent series designations. So the new Scout got series 101, Prince 201, Chief 301 and Four 401. Later versions got the subsequent number, the Prince and Chief got 202 and 302 in 1930,  the four came out in version 402 in -29 and so on.

Those series numbers continued with some changes. In -32 the Scout with Chief frame took over the number 2 from the then terminated Prince and got series 203.

After some years, I don't remember exactly, the production year was incorporated  with for example 741, that series 7 was produced in 1941. Series 5 is Pony and 30-50. 6 is the Motoplane and later Scout, 7 for the military Scout, 8 for the military shaft drive bike. I don't know what series number the Dispatch or Traffic got.

The series 101 was dropped in 1931 and it never was known other than mod.101, but less known is that 102 in fact can be found mentioned in some earlier papers.