The instructions, etc. are still in the box. Stamped on the box is: Model Rectifier Corp. as the distributor. I don't know when they were sold, The instructions call for a 14 x 7.5 prop. For an engine of that size, 25 cc (1.5 cu in) that is a very small prop. That leads me to believe that the engine down on power. Other specs. are: Bore 34 mm, stroke 27 mm, weight 1100 g, power approx. 3 HP at 11,000 rpm. Schnurle scavenging porting. For fuel it says, use normal fuel (even without Nitro). It doesn't mention oil content. One comment of interest in the instructions. Symmetric motor construction, which means constant speed in both directions. Interesting. A hot glow plug is recommended.