|Why is this site called Manufacture Discontinued?
This site is dedicated to the study and appreciation of the
telephone sets made by Western Electric for the Bell System.
The Bell System was one of the most efficiently run technical
organizations ever. Everything they made, everything they installed and
everything they serviced was covered by a printed instruction manual,
these were called "Bell System Practices."
Even though they might no longer make a particular telephone set, the Bell
System would likely still have many of them in service, hence they needed
to have practices which covered them. When a telephone set or part
that was no longer made was listed or shown in a Bell System practice,
they would designate the telephone or part's number with an "MD."
From the name of this site, you can guess what "MD" stood for.
Unfortunately, nowadays, as Western Electric and the Bell System no
longer exist, all of these wonderful telephone sets are now, sadly, "Manufacture
By the way, from this seemingly innocuous one page Bell System practice for
the most common of Bell System telephones, one can still learn a lot of
interesting and important Bell System history.
First of all, we know from this practice that modular 500 sets took over
for the older style in July of 1979.
Also, it documents one variation of sets as having never existed. The C/D in
500C/D really stood for two models, the 500C, which had a dial filler
plate, and the 500D, which was equipped with a dial. (The D for dial is
coincidental, the earlier 500 sets were marked 500A/B.) The sets were labeled
500C/D because they were both built on the same base.
So, when 500 sets went modular, you'd have expected there would have been
500DM sets with dials, and 500CM sets with dial filler plates. However,
this practice documents that 500CM sets were never manufactured.
One wonders why a technical service person would need to know that detail,
but thanks, Bell System, for documenting that information for us to have,