They made like three different 15's. The first one was a real hot reed valve rear carb job. I don't remember the name. But it looked like a Thermal hopper. If you ran it very rich it would, as likely as not, start running backwards on you. It was hard to get started in the right direction in the first place. Needless to say, it ran in either direction equally well.

They had the Tee Dee .15 which was a front rotary valve design that ran a lot more consistant than the reed version. It would only run one direction. Later on, there were R/C versions of this one made.

Then there was another that looked a lot like the Tee Dee but was a cheaper sport engine. It was called the Medalion I think? It was rather mildly tuned. To see one and then see the other sometime later, you would think you were looking at the same model yet when you got them side by side, you would definately know which was the Tee Dee.

The T D stood for Thimble Drone which was the name before Cox and then Estes.

To my knowledge, they never made a 19.

There were .09's in the TD and Medalion lines too.

Jim