Here are some nice cutaway drawings of early 1500 engines.
This one is from the 1961 edition of the VW 1500 Workshop Manual.
I'm not sure of the source for this one, but I think it's pre-production since it has features that were never combined on any production engines, at least as far as I know. It shows a crankcase breather tube, which in some pre-production photos is shown connecting to the air intake instead of the air cleaner. I don't know if this arrangement ever made it into production -- if it did it would have been on only the earliest cars produced in late 1961. The heat riser valve is also pictured, but that wasn't actually introduced on production cars until late 1962.