It's a Kraft 61. Produced by Phil Kraft back in the 70's. Was a great engine and a top performer in FAI pattern. I have a couple NIB I picked up years ago when I was into pattern. Sold the used ones and kept the new ones. They also came with a Kraft carb. One of mine has that carb and the other has the Perry pump and Carb.

Mecoa picked up the rights to the kraft name and all the dies and has been making them for years under the RJL name. RJL is Randy J. Linsalato who owns the company.

One other little item for everyone that badmouths OS because they have plastic backplates. Kraft was using plastic backplates back in the 70's.