This is on ebay and from a seller named diletant2002 who is located in Israel. So far every overprinted stamp I have seen offered by him was forged.
Have a look at the cancel. Two things spring to mind: the date is in a completely different ink and style and the impression of cancel itself looks wrong. Just like being made with a printer. All lines (outer and inner circle) have the same proportions (thickness). That is not so with the genuine cancel. Besides, the cancel on this stamp is from the pre-soviet time. I don’t think they used Zsar cancels in 1929.
The seller writes:
“Since I do not collect or know much about such items, I cannot guarantee that these item are genuine so low starting and sold as is. No refund!!!”
I guess thats kind of fair.