Hi Geoff, from my research I believe you have a Scott Bonnar Model 14 Gang mower. Hopefully Bruce can upload a parts manual to the Manuals area which will throw some more light on the inner workings. Parts are still available albeit a trifle expensive.
The reason I suspect it's a Model 14 is the design of the wheel; if you look at the pics I posted above, you will see that the driving wheel assy are different to yours....
We had a triple gang that used to do the fairways when I was playing golf, I know that the greens-keeper could engage the driving mechanism very easily and the gangs would then have the reel engaged and cutting sending a huge rooster tail of grass sky high as he tore down the fairway.....Ahh memories....
