I’ll say it’s a ’30 – ’38 K-50 thru KA-38 model as it has the spark plugs on the side of the block. the ’39 KA-39 thru the ’48 KD-15 had the sparkers pointing out the back.
I see the plug wires are missing so you might want to see if both of the coils are still in it. It runs on 8:1 fuel/oil mix and yes, it has no water pump.
Looking at it again a bit closer, the gearcase is the KA-37 style so I’m going with ’37 KA-37 or 38! 😉