Well, it might be...
Here are the two images from the listing (Admin - feel free to move above, if required). I trimmed the dark borders a bit, to better fit our format.
In fact, by my calculation (of the weak corner), it might even be an inverted watermark.
Here's what a genuine one looks like:
The Sheriffs concern, and its a very real concern of members here (over numerous threads) is that this is a reckless stamp lister, who probably doesn't know if its real, or not.
If it is real, there are bargains to be had. If its a fake, then buyer beware ..... and despite his impressive 22,000 positive feedback, there are rules that ebay have not announced, that "can favour this kind of irresponsible vendor".
For example, if you leave negative feedback for someone, and they refund you, the negative is struck off.
Its very frustrating, as by my books they did not complete the deal, but there is no downside for them, other than a refund .... hardly a binding contract!
There are also numerous examples of this vendor using shill bidders to realised higher prices. Not in this case (fought over by two snipe bidders in the closing seconds), but we are awash with example of the dubious practices of this vendor.
So, in summary, it may well have been real in this case, and if so, as a lightly used example was good value ..... but can you afford to risk that sort of money with a vendor that neither cares about what they supply, and will be a nightmare to get a refund from?
That's the dilemma of "the wild west frontier of ebay", especially anywhere near "bulk disposers".