It's probably a Kalt Baron/ G-22 series gasser. Take a look at this video I found on YouTube. It says 4 stroke, but I think it's a gasser. The frames look similar. They ran a very slow head speed compared to other helis of the period and also tended to throw a blade now and then in-flight.

http://www.youtube.com/watch?v=IUSkZtg9MjE

Rod