stampgal,
There is a postal stationery card listed for this issue, but the more I look at it, I don't think that's the answer. As you said, the stamp isn't in the proper position and the paper is thin, neither of which is indicative of a postal stationery card.

So... how about this? With regard to the stamp (as opposed to the stationery), Michel lists three main types:
1. Mi 1 -- The basic, postally used issue, perf 11 1/2.
2. Mi 1U -- Imperf, never postally used.
3. Mi 1N -- A "Neudrucke" (new printing), never postally used, no gum, slightly lighter color.

You could have a corner piece from an imperf sheet. If it doesn't have gum, it's likely the Neudrucke.
Also, the "cancellations" appear to be someone testing a modern date stamper rather than trying to legitimately cancel the stamp with a correct canceler for the period.