Your question has been asked and answered, markus.
This is the engines forum, where motor heads hang out, brag a little, and answer "what is it?" questions.

This is where the real pearls of information/facts are revealed, in the side bar conversations that make an often asked question, come alive.
For instance, did you know about the OS series V engines? Only the old guys usually remember them, but know that you have been fed a pearl, and that Fox won't be the last engine you'll ever acquire.
Next time you are perusing the engines swapshop, and run across an OS 40 FSR, or 45 FSR for a good deal, you'll now know to swoop down and beat us to it.
For me, I just love it when a question I ask goes sideways and seems to take a personality all it's own.
I determine that it's a sign of respect when very experienced modelers take the time to participate in any thread I start, whatever their comments be.
To me, you were asking a "What's it worth?" question more than a "What is it"? question, as FOX is emblazoned on the crankcase.
You had two people answer you:, from $25-50.00 and others would take it for free if you sent it to them.

I hope that you will take this advice in the spirit in which it was written, that is to lighten up and listen up. I have consistently learned more from what others have posted to than to my own questions.
Best to you,