Any tips to help find an impressed mark on porcelain?

Hi,
I've recently purchased an early 19thC porcelain plate that was sold as unmarked , but have come across the exact same item in an auction catalogue , and an old museum exhibition catalogue  (both from several years ago) where they both describe it as having a faint impressed mark....
For the life of me I can't find the mark at all!

This is what I've tried so far without any success;
Scanning the base with a computer scanner in the hope it would detect the mark.
Holding plate up to extremely bright light source (incandescent bulb and LED types, and  a UV black light lamp) , the porcelain is quite translucent, was hoping the mark would be visible in outline.
Holding at an angle in natural daylight.
Using a magnifier stand with a built-in light.

Now, I don't doubt the identification of the item at all, but I'd love to see the mark just for peace of mind.
I think the problem is that the glaze applied to the piece has filled in the impressed mark that probably wasn't very deep in the first place.
Can anyone offer any advice as to how to find this mark?
I spent about an hour looking at the base, and the only thing I can see is an area that is lower than the rest of the plate base and possibly 1 letter of the name , which *might* be the name filled in with glaze, though of course it could be wishful thinking?
It has also occurred to me that both the Auction house and museum might have been fibbing about it being marked!
I'd be very grateful for any help.
Thanks!

Thanks!
Luckily I'm not long-sighted and close-up my vision is excellent.
I totally agree that often holding at an angle will enable marks to be seen ; My mum once bought an "unmarked" piece of Moorcroft that when held at the right angle the name could definitely be made out.
The one letter that I can see on my plate (or is it a random blob,lol) is indeed in an area that could have other letters there too.......
The more I think about it though the more I'm thinking about auction standards.....
When an auction house describes a lot do they just take the vendors word on marking etc?
If the vendor says it is marked then will they just accept that and describe it as such?
My plate was exhibited at a museum where one of the exhibition organisers also happened to be the then owner of the plate!
I'm beginning to wonder if in both cases the owners , for whatever reasons, said it is marked, when it isn't!

I find sometimes that if I take the best picture I can at the highest resolution and then open it in Photoshop or similar programme - then play around with the brightness and contrast (perhaps even convert it to black and white) it can sometimes make marks/potential marks clearer.

You can also rotate the image slowly and see it anything looks promising.

Johners2000 wrote:I find sometimes that if I take the best picture I can at the highest resolution and then open it in Photoshop or similar programme - then play around with the brightness and contrast (perhaps even convert it to black and white) it can sometimes make marks/potential marks clearer.

You can also rotate the image slowly and see it anything looks promising.

Thanks!
TBH I really hadn't thought of that! I will give it a go.
I think that the one letter that I thought was the mark might well be the location.
Holding at an angle in strong daylight it's apparent that *something* could be impressed there though it's stretching credibility IMHO that the full mark can be seen as claimed by the 2 old information sources!
The other thing I was going to try was to place the plate (briefly) in front of a powerful halogen floodlamp!
I was thinking that any impressed mark hopefully would be visible through the translucency of the porcelain body....