The engine is looking pretty good. It probably wasn't made at numerous locations and different factories like the MK-17 was. So maybe the quality is better.

I think what was cool about these rear intake rotary valve engines was how some of them got converted to four stroke engines. It sort of made it easy to convert them.
Granted you needed a new cylinder sleeve, head, and backplate as well as valves and a gear train and cams. But it was pretty cool to see some that were made into four stroke engines.