One of the earliest pony libraries was the Crown Pony Series, which featured titles published by the Lutterworth Press. Lutterworth published titles in various libraries (the Dominion Library was another) and it isn’t particularly easy to work out in what edition a title first appeared, or if it was in the Crown Pony Library when it did. It’s also quite difficult to work out exactly how many titles were published in thePony Library: they appeared both in hardback and paperback. As far as I can see, most titles were published between the mid 1960s and 1970s. The numbering doesn’t seem particularly consistent; Pony Girl being listed both as Number 4 and Number 21.
The Lutterworth titles were mainly by authors who were in the second rank. The titles are generally good solid reads, but Monica Edwards or Ruby Ferguson they are not.