You are correct, Jim. To my knowledge there were no Holland or Atwood .061 Wasps. They did make .051 Shrieks, I think.
However, we were talking about the AP Wasp .061, an import from China. With a control-line venturi modification, it is the best small stunt engine I know of. 20K on 10% fuel with a 5.5x2.5 APC prop. It flies 230 sq.in. planes with ease. it is also the ONLY small engine I know that has a bronze bushed crankcase. Lots of data on them in the 1/2A forum.