A scan of the stamps back would help but from what I see so far here goes.
1) You say you have the anchor watermark, this is a start to a real CGH stamp. Also the secret engraving marks are in your copy.
2)The cancels shows to be real as it has the correct lines and the C G H letters. (see following picture)
3)As long as the paper does not have blue tint to it it gets narrowed down to a Scott# 4, 4b, 4e or a 13, 13a.
4) Stamps printed by De La Rue & Co. should appear fuzzy or lightly printed for a Scott 13, or 13a.
5) They copy shown appears to have crisp engravings and well defined printing making me lean towards it being a 4, 4b, or 4e.
6) So in my opinion a 4, 4b, 4e it may be leaving the color to determine.
7) I would lean to a Scott# 4e as it appears a bright blue. Stanley Gibbons lists this as a SG6 deep blue.
8) Also it appears to be a die (A) because of the thick lettering.
Note* Please keep in mind that scanners and computer screen settings come into play when looking at a stamp on the net.
See the G and faint lines of the H
