Yes, there you have it a old RC class B combat for up to .29 engine size.
Fox made the Combat .29 as both a RC and a control line or free flight engine too.
Then they made the .36 combat for the next size up as well in both RC and CL.
Later I think Fox had given up on the combat engines and instead of scrapping it out, they bored it out and made a .40 engine out of it. That is were it stayed ever since.
Fox had for many years kept modifying and improving the combat engines, but eventually the engines just were not selling as well as they used to. The larger Combat engines and planes were becoming less and less popular over time. So sales were dwindling as time progressed.
Here is a short history on the Fox combat engines
http://www.clcombat.info/foxhistory.html
I think he made the combat engine series from 1957 up until maybe 1990 or so.
Unfortunately Fox had trouble with AAC cylinders in the last MK 7 engines. But his MK IV through MK VI engines pretty much ruled combat from 1983 through 1986 or so.
Then it was the Nelson, Cyclon,Fora and some other engines that took over being the engines to get. Of course Nelson is out of the picture now too.