There are some forgeries among the items presented in the current auction.
The first two items got fake overprints. The Jemchouchin signature is probably faked too.
Both stamps were not available at the time in the post office stocks. They can only exist as so called “over the counter” productions. If genuine, a very rare stamp. In this case both overprints are crude forgeries. You can find posts on my blog with details about the genuine overprint.
This is one of the typical “I got old paper from a worthless cover, lets add some stamp paint some cancels and see how much we can get for it”. The Erivan cancel is such a crude forgery, no professional auction house should have a problem seeing this.
Another of the “lets us some old paper I found” forgery. This time the 1K manuscript overprint is forged as well as the cancel. I would expect a professional stamp dealer to be able to spot this.
In the description you can read “reprints”. This is correct. This also means, those stamps are forgeries. They are worthless and should not appear in an auction. Same story with the sheets in the lot before.
Collections are always dangerous. In this case, and there are three more pages almost all overprints are forged. Perhaps 5 to 10 stamps are genuine.