Help With GB King George V

So I hoping someone can take a look at this one for me. I think it's SG428. The wmk has a little confused though. It does not look like W111 to me, but W11a. BUT, I do not see SG428 with W111a. Can anyone tell with the below picture? best I could do for the Wmk - the image is looking at the back of stamp, top up. Tks much.

SG428, Watermark "Block Cypher."
his stamp does not exist with W111a.

Edit: W111 is the SG Concise reference for a watermark known as "Block Cypher." The specialised number is W15. W111a is a similar but smaller type used for experimental paper used by Waterlow in 1924 and 1925 for some printings of the 1d and 1½d "Mackennals." It is specialised number W16.

That's why I was confused and asking. So you're saying mine is SG428 with W111?




I don't have my Concise in front me of, but, was wondering if you could also explain this : I believe it mentions the difference in horizontal spacing in rows of 111a vs 111 to be 12.5mm vs 14.5.

What exactly are they measuring? I don't get measurements close to that. Thank you.

EDIT: OFF TOPIC -




Where do you get the specialised number from? I've been looking for a more detailed SG catalog and seems like they have not printed a more updated one for surface printed stamps in a while. I THINK vol1 from around 2011?? Thank you again.

SG "Kings" catalogue -

https://www.dauwalders.co.uk/gb-spe...ion-138580-p

It should be the vertical spacing of the watermark. So, from the bottom of the cypher to the next one,

Volume 1 is a Queen Victoria specialised catalogue. This has been split in a part 1 issued in 2020, and a part 2 that was planned for 2021.
The stamps of Edward VII, George V, Edward VIII, and George VI are listed in volume 2. It, last, was published in 2015 and was reprinted, but has been out of print for some months now. Dauwalders (see link provided by GeoffHa) does not have it in stock either.

So I do t have the catalogue in front of me now. But I know it mentioned difference in horizontal spacing. Must be a misprint. What is meant by 'cypher' - letters , crown or whole mark?

So mine must be SG428?

In mine it reads 'closer spacing of horizontal rows.' It is somewhat ambiguous.




The "GvR" part.




Yes,

either way, 12.5 to 14.5mm is a lot. I cant get that to match up period.

tks too on the 428 ID