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GPO telephone base code decoder

Find out when and where a GPO phone was made

This tool decodes the GPO code stamped on the base of vintage and antique telephones to give you its year of manufacture. You will also be given the company and location of manufacture, any details I have about the model and a link to its possible resale value. The format of these markings has varied a bit over the years, some digits may be omitted so you should leave those blank. In some cases they are split across 2 lines but you should be able to figure out which goes in which box. The boxes outlined in red are compulsory and should be present on most phones, if you are having trouble start by filling in the red boxes and the rest should become obvious. Other markings should be ignored including any numbers inside a box labelled 'P.O. SAMPLED'. This tool should currently work with models from the 1920s up to the 1980s trimphones. For phones which have been repaired or refurbished you may find 2 codes, you should decode them both and the earlier one will be the manufacture date.

Here are a couple of examples from my own GPO phones.
gpo 706L gpo trimphone


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