black boxes are the older ones the red boxes are the newer models.webra had the blackhead 10cc back in the late 60's a powerhouse at the time.it was a loop scavanged engine,had a baffle on the piston.about 1973 plus or minus a year they came out with a new blackhead .61 it was schnurle ported,at the time it had a 1/4-28 crankshaft stud,later it was changed to 5/16 .at the time both were side exhaust ringed engines.