Sg 185 ,1£ Brown- Lilac Stamp - Forgerie?

Hello.
Would you coment this SG 185 ,1£ brown- lilac stamp.
It's for sale on big website fir online trading. The seller wrote that he both it as a forgerie, but does not know whether it is a forgerie or original.
The reason for his doubts is tath the stamp has watermarks on it and it is a good material for research from philatelists as he said. The price asked for it is much lower then other SG 185 stamps ,but he is still asking a substantial sum for it.
Could you tell from the images is it real or fake ?

It is a picture of her after raiding the fridge.

This is what it should look like

The watermark shows that it is a forgery. The genuine watermark, which the Stanley Gibbons catalogue designates as number 49, Imperial Crown, has the two sides going from bottom to top, going upwards in a continuous straight line at about a 15 degree angle from true vertical, and on top, the cross is a simple tiny one made up of just two crossed lines. In this one, the crown is pinched in on the sides, and the cross is larger and is more of an outline, more two-dimensional than the genuine watermark

The watermark is as clear as a cancel when looked at even from the front of the stamp and without being dipped. An overzealous application of pressure one might say. More is better said the forger!

I am having a real "moment" here
That Watermark (The image at least) is GENUINE
I recognise it very well, but dashed if I can find it listed ANYWHERE.

Sheesh
Can someone put me out of my misery?
I know it as Wmk 13

Perhaps it was on that Escutcheon seal stamp perhaps ? Cyprus?

I checked Barefoot Revenues without success.

Any members able to suggest Watermarks being shown in old catalogues ?
Hendy etc?
(Saves me trolling through 30 catalogues)

Found it
Watermark 13
https://goscf.com/t/51650#448007 br /

Still not aware of what stamps used that impression.

Maybe referred to as the "Globe and Cross"?

Waddsbadds ,tank you for your precise answer.
The reason to ask was to know if the stamp and the watermark on it are genuine.
As l'm not an expert in the subject it's very difficult for me to determine whether the stamp is a forgerie or not.
I agree with wath rogdcam wrote about the stamp.
l have also observed that the watermark bulges of on the paper .
The watermark is not visible in front of the stamp.
This is clearly seen from the image tath NSK posted .
It most likely a very good forgerie .

I have a green version of this stamp with a watermark so faint it is barely visible. It's used so I'm convinced it's real.

That is a forgery .....just like one of mine .

The watermarks aren't aligned either.

The background network around #1 is a clear gave away as a forgery I think.