so 50 is good deal..

now WILL this thing work as a rear tcase with a mc07 marlin dual case adapter ?

$50 is a great deal for any RF1A toy gear driven t-case, let alone one as rare as that one. Marlin has the only two PTO cases in the US that I have been able to find reference to so far. And there is a guy in N.Z. that has one, and he said that they are pretty rare over there too.
  It should work fine behind a crawl box, marlin is, (or was) running one in his truck.