New York: Bell Telephone Laboratories 1950. First Separate Edition. 4to., pp. 7; original printed wrappers; ex-library stamp (dated Nov 21, 1950); perforations for ring binder as issued; near fine. First separate issue, October 1950. Originally published in the Bell System Technical Journal Vol. 29, pp. 343-349, July 1950. The Bell Telephone System Technical Publications Monograph series was primarily distributed to libraries that subscribed to the series. Near Fine. Stapled wraps. 
"In discussing the memory requirements of a telephone exchange, Shannon derived a 'Separate memory" formula, M=2SlogN, which he interpreted in terms of information theory" (Origins of Cyberspace 883, quoting Shannon 1993, no. 56).
First printed in the July 1950 issue of the Bell System Technical Journal, this Monograph was issued in October 1950. Often erroneously referred to as offprints, the Monograph series was not published in most cases contemporaneously with the original publications. The series also included work by Bell System employees that were first published outside the Bell System umbrella. They are, however, usually the first separate publication, and are thus highly prized by collectors since offprints in the traditional sense were not produced in the Bell System as far as we are aware.
Shannon Collected Papers #56 referring to the Bell System Technical Journal (not Monograph) issue.