Ty, the Pope rotary valve 2 stroke engine was from the late 1950s as I recall. I'm not really sure, but I thought Pope may have made it themselves in Australia. The engines had a certain popularity on very early go karts here.

Also, as far as I can tell from internet reports, in general the Wisconsin Robin engines are Japanese Robin (i.e. Subaru/Fuji Heavy Industries), sold by Teledyne in the US under their Wisconsin brand. Most Robins are 4 stroke, but they also made 2 strokes. Fuji registered the Robin brand for their industrial engines in 1960, and made a sales agreement for the US with Wisconsin in 1971. You can read the history here:
http://www.subaru-robin.jp/what/text2/jigyoubu.htm

For interest, see this workshop manual:
http://www.jackssmallengines.com/pdf_documents/robin%20engines/Manuals/TTP30084.pdf

It doesn't seem to be the same as yours in detail, but may be similar.

So, you have a very decent engine there. Fuji/Robin is the world's fourth largest engine manufacturer, and Japan's second largest.