Dell began using an unorthodox numbering system in June 1962. From Lyles, PUTTING DELL ON THE MAP, at 53:
Dell's numbering system changed considerably in June, 1962. Replacing the series numbers were 4-digit IBM numbers, assigned by a computer, which projected where a given title would fall in an overall alphabetization of all Dell titles. Thus, Abstract Painting was #0012; The Looking Glass War #5024; The Young Lovers #9856. But the system proved less than perfect: #4893, James Dean preceded #4903, The Lodger, and #5000, Angelface. (The random, non-chronological numbering system frustrates potential collectors of these later Dell books.) In 1977, Dell began using 5-digit IBM numbers (a "1" or other number added to the previous 4-digit number), which were in turn incorporated into a title's ISBN number. From 1962 to the present, the IBM number assigned to a title remained the same, regardless of reprints or revised editions, unless a title change occurred. A given book thus became easy to track.
Dell, Publishers of Magazines and Reprints, PW, May 19, 1945, at 1990-1993 (25th anniversary piece).
Dell Shifts Distribution to Independents from ANC, PW, May 6, 1957, at 19.
Dell Building New Eastern Shipping Center, PW, Mar. 29, 1965, at 28 (with architect's rendering of building; this is the building as of August 2019).
Eileen Lottman, Helen Meyer, PW, Mar. 6, 1972, at 24-26.
William H. Lyles, DELL PAPERBACKS, 1942 TO Mid-1962: A CATALOG INDEX (Greenwood 1983).
William H. Lyles, PUTTING DELL ON THE MAP: A HISTORY OF THE DELL PAPERBACKS (Greenwood 1983).
The Mapback Index, www.mapbackindex.com BEST EXAMPLE OF HOW TO DESIGN SITE
Clark Evans & Colleen Stumbaugh, A Collection of Value: Mass-Market Paperbacks at the Library of Congress, 17 BOOK & PAPER GROUP ANN. 57 (1998), available at https://cool.culturalheritage.org/coolaic/sg/bpg/annual/v17/bpga17-08.pdf.