ORIGINAL: RC-Bearings
There was another OS engine back then that was popular called the Hanno Special, named after Pattern Ace Hanno Prettner. IIRC, it was one of OS first nickel plated cylinder models and there were reports of peeling even back then. It was a powerhouse engine designed from the SF for pattern. It was ported for tuned pipe use and won a lot of contests. rc-bearings
the only engine that i know of that the classic pattern forum guys here are trying to build a serial number data base on. probably the most discussed engine here.