How do I tell if something is genuine?

I own the below watercolors and with some research I found that they are the following:
https://www.tate.org.uk/art/researc...-datur-hora-quieti-for-rogerss-poems-r1133387
https://www.tate.org.uk/art/researc...turner-loch-lomond-for-rogerss-poems-r1133369
I don't expect the ones I have are genuine seeing as the Tate has both of them but how can I tell if they are old or worth anything?

 

They are probably not watercolors, but color reproductions. If they are old, they may be chromolithographs. If later, there may be a tell tale dot matrix pattern visible at extreme magnification, as you see in this image:


If they are modern, which I sort of doubt, then it can be hard to tell.

There are many different ways to reproduce a picture. Telling which applies is not necessarily easy.

 

FYI in the late 19th century chromolithography was popular. Unlike later offset printing, these often don't show any printing dots at all as Moreotherstuff noted. Some can be very convincing!

Not saying your pieces are definitely chromolithographs. Chromolithography - Wikipedia

 

if the Tate has em....these are nice decoration.......worth little..

 

What size are they? Could they be postcards?

 

I was switching back and forth between your images and the museum ones and there are some distinct differences. This would lead me to believe that yours are lithographs, as the image would have been redrawn using the original as an example. They look like something that would have been sold in a museum gift shop. They are nice looking pictures and frames.

 

That's very interesting. I wonder how old Gould's images are? If they were sold at a museum gift shop, is there any way to determine age of the prints or the name of the museum? The Tate? Whoever bought them probably enjoyed the originals.

 

So I found out more about the above. They are J. M. W. Turner's Vignette Drawings, first series. They belong to a book of drawings as per the below attachment. Someone must have removed them and framed them individually.
https://www.abebooks.co.uk/book-search/title/turners-vignette-drawings/author/turner/

No idea on value though.