Quote: tony_k_1965I notice on the 1966S version there is a wrong alignment type, this I didn't know about (must check all my 1966S shillings now). Also Zac could you tell me which book that it is you're using please.

I have two books for UK coins, by Rotographic - the shillings are from the pre-decimal 'Collectors' Coins GB' 36th annual edition 2009. The decimal coins are in 'Check Your Change' 2008.
Both written by Chris Henry Perkins, and the company runs the forum predecimal.com
As you see, when I get a book like the 2009 one, I highlight the more valuable ones, so I know to look out for them. Here are some (I exclude many Victorian varieties, and 1937) from that book ...
Farthings
1915 BRITT [no gap] as normal coin is BRIT T with gap
Half Pennies
1902 Low Tide
1925 Modified Effigy (to stop 'ghosting')
1957 Calm Sea
1958 thicker rim, shorter teeth
1965 mule - New Zealand reverse
1967 wide rim
Pennies
1902 Low Tide
1903 open 3 [bottom serif points at the '0']
1909 '1' is directly above tooth
1912H and 1918H 1918KN 1919H 1919KN
1920 colon after IMP points at a tooth. Extremely rare
1922 centre trident prong well below tooth
1926 Modified Effigy
1933 of course
1940 double exergue line
1944 unconfirmed sightings with waves reaching slightly into exergue
1945 doubled 9
1950 1951 1953 scarce
1952 and 1954 excessively rare
1955 to 1960 none minted
and so on, for other denominations ...
P.S. Somewhere I heard about a very rare 1947 Shilling that was made in silver. All silver UK coins are well-known as "pre-'47" but a handful of the English version were made of silver in early 1947, apparently.