The cylinder has this cast in to it.
447N18
W2
++
MAHLE
and 3.2 ink stamped on th top fin.
The carbs are Walbro WT76A.

I've got pictures but I'm getting an error on uploading them, I'll try again later.

Pictures.

There were several 50's made with this very popular jug

Namely the Brisson but also the Fox etc.

Looks like a Early Brison or late A&M 3.2. Its been reworked to have the Syncro Spark ign on. Note new timing ring and lack of pushrod to it from the carb.

I think it is a Brison 3.2,but I could be wrong.I was once but it's been a long time ago.Good engine if it has a factory crankshaft.
BCCHI

I agree w with tkg , a walker or a&m (a&m was bought out by Brison)

Thanks guys.

I'd say A&M, before Brison took over. That's where gary got the case layout. The timing ring is in the wrong place for even an early Brison, and his carb installations were a lot cleaner.