There are minor varieties of these but the only one that really is worth a premium is the 1946 ONE flaw (dot). There is a raised dot after the E in ONE that is easy to spot if you find one and scarce /rare in grades of EF +. Another worth looking for is the 1944 with the last 4 over a tooth and the top to centre of the wave. You can also get all three that have missed the mint toning and are a normal colour rather than dark ,although you really need them in high grade as the hypo they were dyed with can ware off over time. The varieties mainly are recut digits and really need to be seen in hand. Millions of all three dates and are common unless you have a GEM that will look really glossy as if only minted yesterday.
The initial book I recommend is Collectors coins Great Britain. If you are serious a copy of Freeman and I respectively suggest a book on grading UK coins. All these are published by Rotographic (from Predecimal.com or Amazon)