Agreed. If anyone is interested in breeding, or standard bred Rocks in general, the Plymouth Rock Breeders Thread is loaded with great information and discussions. Heres links to a couple books I found either on that thread or another, I can't remember, if anyone is interested. The first is the
Plymouth Rock Standard and Breed Book and the second is another book discussing the varieties and standards. They're old books, from 1915 and 1911, but still provide a lot of useful and interesting information in my opinion. Hopefully the links work.
The Plymouth Rock Standard and Breed Book;
A complete description of all varieties of Plymouth Rocks, with the text in full from the latest (1915)
revised edition of the American standard of perfection as it relates to all varieties of Plymouth Rocks.
Also, with treatises on breeding, rearing, feeding, housing, conditioning for exhibitions, exhibiting--etc
https://archive.org/details/plymouthrockstan00amer_0
Standard-Bred Plymouth Rocks, Barred, White, Buff, Silver Penciled, Partridge and Columbian;
Their practical qualities; how to judge them; how to mate and breed for best results
https://archive.org/details/standardbredplym00denn