The Japanese-made ROC .049 of 1950-1954 displays a very obvious design influence from the contemporary OK Cub .049 models. This well-made little engine was among the very few Japanese 1/2A model engines to appear prior to the late 1950's. This is in sharp contrast to the situation in America and elsewhere, where 1/2A engines in the 0.049 cuin. (0.81 cc) displacement category were viewed as the ideal entry-level and sport-flying powerplants, hence making up the majority of model engine sales during that period. It appears that Japanese modellers adopted the 0.099 cuin. (1.62 cc) displacement category as their standard entry-level and sports displacement class, since every significant Japanese manufacturer produced models in that displacement range while almost universally ignoring the .049 cuin. category. The ROC .049 was thus very much an exception, presumably being targeted primarily towards sales among members of the perdominantly American forces of occupation.
A full description and test of the ROC .049 may be found on Ron Chernich's "Model Engine News" (MEN) web-site.