I think you will find that this motor is most likely a model 20. Without being able to see the front of of the powerhead, I can’t verify that the crankcase vents exist. Model 30’s would have that feature.
What makes me suggest that this is a model 20 is that a Model 30 would NOT have the variable pitch prop as the one in the photo does.
FWIW the model 20 was sold with cylinders that had the dual spark pug locations as well as the more conventional cylinder with one plug location only. I’ve got both in my collection.
Hope this helps.
Best,
PM T2
He's livin' in his own private Idaho..... I hope to go out quietly in my sleep, like my grand-dad did..... and not screaming, like the passengers in his car...