Great Britain 1-D Queen Elizabeth 1952-1955 Difference

I am waiting on my fist Stanley Gibbons book, the Great Britain concise catalogue and was wondering if this info will be indicated inside.

From the website I am checking, I can't see the difference between both Queen Elizabeth stamps 1d. One was made in 1952 and the other in 1955. Both have the same color according to the website and the same perforation. And it is not the only one which seem to be duplicated.

What is the difference between them and will this info be in the book?

Thank you in advance. :)

The stamps from 1952 have the Tudor Crown watermark (SG 153), while the 1955 stamps have the St. Edward's Crown watermark (SG 165). This is set out clearly in the GB Concise Stamp Catalogue, with illustrations.

Great, Thanks!