Tom,

Have just checked our two No 2s and they both have 11 tooth gears,  Presumably a 13 tooth gear would need a different bull (the main wheel gear) gear???  I  wonder what the earlier Parrets had?  Is the one with the 13 tooth gear an older No. 2?? 

The elder of my two has different front and rear hubs to the younger one and the same as the earlier Parrett - which is how we have concluded that it is the elder one of the two because neither have serial no plates

John