The OK diesels represented one of the final attempts by an American mass producer of model engines to market the compression ignition concept to the American public. The first OK diesel models appeared in early 1953, more or less concurrently with the advent of the competing McCoy .049 Duro-Glo diesel model. Interestingly enough, neither of the original OK offerings had the same displacements as the far better-known .049 and .075 cuin. models which came later. Those initial diesel offerings had displacements of 0.061 and 0.149 cuin. respectively. They were introduced with some fanfare in April 1953 but were not promoted with any fervor thereafter and were not manufactured in large numbers. Surviving examples are extremely rare today. 

These models were soon replaced by the familiar .049 and .075 cuin. models which are illustrated here. These light, compact and well-made little engines were notable for the very ingenious "shock absorber" system which was built into their cylinder assemblies in an effort to minimize shock loadings on the working parts during operation. They also featured contra-pistons which sealed with O-rings. Once one got used to the feel of this system, the engines started and ran very well indeed by contemporary standards. Despite this, they did not find lasting favor with the American modelling public, being phased out during the latter half of the 1950's. 

The full story of the OK diesels may be found elswhere on this website.