Originally Posted by
buzzard bait
The 60 II and the early 60 III types for RC had holes in the sides of the exhaust for an exhaust baffle.
All of the RC 60-II and III had the holes for the exhaust baffle. These were dropped with the introduction of the 60-IIIB but there's a trap. Some of the early 60-IIIB's were built using the RC 60-III crankcase so they look like a 60-III. The only way to tell it's really a IIIB is that it'll only have a single ring instead of the twin rings of the earlier type.