Most phones have markings on their bottoms that provide important, or useful, or merely interesting information.
Similar identification schemes were used by
the major manufacturers. HOWEVER, sometimes the same number was used for different models made by different manufacturers; and some codes were not used by all makers.
The date code format varies, but should be pretty obvious, such as:
- "9 (space) 82" for September, 1982
- "1-70" for January, 1970
- "82-10" for October, 1982
- "3/78" for March, 1978
- "82003" for January 3 (the third day of the year), 1982
It was common for phones made by ITT (and perhaps by other manufacturers) to be dated six months after the actual manufacturing month, assuming it would take
up to six months for the phone to reach its ultimate customer. This way the customer assumed the phone was brand-new.
When a phone was taken out of service and refurbished to be provided to another customer, it got a new date, either with a stick-on label or with ink. The earlier date could be covered by the label or paint. When phones are
refurbished, they usually include parts made at different times. Many individual
phone components have dates on them. When a phone was refurbished as a different version of the original model, a label indicates the new version.
Model numbers are usually obvious, such as 500 for a common rotary-dial desk
phone or 2565 for a six-button touchtone desk phone. Sometimes the number sequence also indicates the color, such as the "13" (beige) in the top-left photo.
Letters after the numerals indicated specific versions or features, such as:
- M, for modular cords
- G, polarity guard on touchtone phones
- P, wall phone with modular plug on its back plate
- W, Western Electric phones without Bell System markings, made for the
military, railroads, or non-Bell phone companies
- CS, phones owned rather than rented by customers
- BA, standard ringer
- LR, no ringer