Penguin Collectors Society

The quick answer:
Generally anything with the word Penguin, Puffin or Pelican is a book published by Penguin; there are several different series within each of these brands. In addition the names Porpoise, Ptarmigan and Peregrine are also published by Penguin.

The slow answer:
Penguin books have published under many different banners, some of which were developed in-house and some which were bought, like the 2002 purchase of the Rough Guide books. The in-house developed series tend to keep the bird theme and while there is much to be applauded in the more recent publications, the Society's interest naturally tends towards the early series and the early to mid twentieth-century book design.

In the first 30 years of Penguin books, there were 80 different series, and as well as official Penguin publications there is a large amount of ephemera connected to both Penguin Books and the Lane brothers. This is, therefore, not an exhaustive list of these early Penguin Series, but it does contain the best known series and is a good place to start in order to begin to understand the wide-ranging focus of Penguin publications and find out if the books you own are published by Penguin. The letter codes used here are those developed and used by Penguin for the different series they published.

Series Code	Series Names	Information
	Main Series	Fiction: the first 10 books were published on 30 July 1935. The covers were colour coded by genre.
A	Pelican Books	Non-Fiction: the first Pelican was published in 1937.
AB	Pelican Shakespeare
AC	Pelican Classics
ACO	English Language Book Society
AL	Allen Lane the Penguin Press
AP	Penguin African Library
AU	Australian Editions
B	Penguin Shakespeare	Drama: 37 volumes published between 1937 and 1959 containing the complete works of Shakespeare.
BE	Buildings of England
BP	Baby Puffins	Children: 9 books published for very young children between 1943 and 1948.
C	Penguin Illustrated Classics
CAF	Contemporary American Fiction
D	Penguin Poets
E	(1) The Things We See
E	(2) Planning Design and Art Books
EL	Penguin English Library
F	Editions Pingouin
FR	Penguin Film Review
G	Penguin Guides
H	(1) Penguin Hansard
H	(2) Horwitz editions
Hxxx	Library Editions
J	Porpoise Books	Children: 4 hardback books published in 1948.
K/KP	King Penguin Books	Non-Fiction: 76 colour illustrated hardback books published between 1939 and 1959.
L	Penguin Classics
MM	Penguin Music Magazine
MP	Penguin Modern Painters
N	New Observer's Books
NB	New Biology
NP	Penguin Modern Playwrights
NS	New Penguin Shakespeare
P	Pelican Books USA
PA	Topolski Prints
PC	Puffin Cut-Out Books	Children: a small number of cut-out model-making books published between 1947 and 1953. Unusual to find 'uncut'.
PD	Penguin Parade
PE	Puffin Explorers
PH	Penguin Handbooks
PK	Peacock Books
PL	Penguin Plays
PMC	Penguin Modern Classics
PNW	Penguin New Writing
PP	Puffin Picture Books	Children: Penguin's first children's series, 120 larger-format titles published between 1940 and 1965.
PR	Penguin Prints
PS	Puffin Story Books	Children Fiction: Penguin's main series for children first published in 1941.
PT	Ptarmigan Books	Children: a series of 9 books containing games, quizzes and puzzles published between 1945 and 1947.
PX	Picture Puffins
PZ	Pelican History of Art paperbacks
Q	Miscellaneous	Non-Fiction: a mix of books that did not belong anywhere else, first published in 1942.
R	Penguin Reference Books
S	Penguin and Pelican Specials
SC	Penguin Scores
SE	Services Editions
SH	Penguin History of Britain
SL/PSL	Penguin Shakespeare Library
SN	Science News
T	Transatlantic
V	Editions Penguin
WA	Penguin West African Series/African Series
X	Penguin Education
Y	Peregrine Books	Education: academic books, published between 1962 and 1989.
Z	Pelican History of Art	Non-Fiction: originally large, hardbacks with dustwrappers and, initially, cardboard slip-cases; later reissued in paperback; first published in 1953.