Steve,
I cannot help you with the Gibbons numbers as my catalogue only goes up to 2000.
I can tell you the letters from your scan although this is only a part set you show.
The sheet of 22, issued Tete-Beche and was 'accompanied' by another sheet of 10 [also Tete-Beche] which showed the letters 'Sofit'. 10 of the Hebrew letters are written differently when at the end of the word although the name is the same. Hence one says 'mem' and 'mem sofit'.
Anyway, from top left; Lamed,Mem,Noon,Samech,Ayin,Peh.
Second row; Caf,Yud,Tet,Chet,Zayin,Vav.
In Hebrew, one reads from right to left so the names I have written are not in alphabetical order !

Are you confused yet ?
If you need any more from this lovely set, just holler.
The other stamp is a State Revenue, but have no idea of year. The value on the stamp is 10 agorot, probably the lowest value issued.
{I will try to check}
Hope this helps a little.
Londonbus1.
PS My spelling may be different than Gibbons !