Upvote:2
The new red box, as modelled by George Osborne in the OP's picture
It appears to be Queen Elizabeth II's coronation monogram:
https://i.ucoin.net/coin/2/482/2482448-2/guernsey-50-pence-2003.jpg
https://commons.wikimedia.org/wiki/File:Royal_Monogram_of_Queen_Elizabeth_II_of_Great_Britain.svg
I do not know why this variant was used. As MCW pointed out in the comment, red boxes are bespoke and the decision may have been purely aesthetic (but I speculate).
Gladstone's red box
The description on the website of National Archives does not mention the cypher, but I think it is Queen Victoria's monogram. Click on the link below the picture and zoom in. The sharp downward point of the V is visible.
For comparison:
https://i.ebayimg.com/images/g/7UAAAOSwrDxfu57u/s-l500.jpg (from https://www.ebay.com.my/itm/1888-Book-Owned-by-HRH-Queen-Victoria-Special-Prize-Binding-ROYAL-Cypher-VR/143861341886)