Petter type AS questions

I just recently acquired a Petter type A engine. It is purportedly a type AS; I am wondering if someone can enlighten me as to the features which distinguish a type AS from a type A. The engine seems to be in pretty good nick overall; it runs although it took a fair bit of cranking to start. Sadly the tin-work around the head has been replaced and the builder's plate was lost. As well the original fuel tank has been replaced with a rectangular black plastic affair - at least that won't rust.

The carburettor is a Zenith which probably needs a good clean but seem to be in good shape; no excess play in the throttle shaft. The link between the governor arm and the throttle is absent, as is the original silencer. The mounting ears are not part of the crankcase casting; the crankcase is bolted to a flat bed-plate of which the mounting ears are part. I have not noticed this configuration in any online photos or videos I have seen, and I wondered if this in itself was a feature of the type AS.

I know that Petter type A engines are as common as dirt in the UK. However this is quite a rare and exotic find in my part of North America (West Coast of Canada) and I am well chuffed. Given how common the Petter type A seems to be in the UK I am surprised how little online information seems to be available.

Thanks for your consideration,
Grant McGregor

The AS was really just a standard A Series engine but governed to run at a higher rpm, and therefore higher horsepower. They were mostly assigned to the military and these will likely have a brass WD (War Department) tag on them somewhere (see here). The higher rpm meant they used more fuel, so they were often fitted with a high capacity tank too.

Another thread suggests that they were fitted with a wider flywheel, but most of the ones I've seen had a standard width flywheel, so perhaps it was just for certain uses.