Here we have for sale a genuine original GPO Trimphone (model 722/2) from the 1970's. The phone is tested working and the dial operates correctly, this one has been converted to the standard BT style plug so should just work (bear in mind these phones are pulse dialling only).
The ivory coloured plastic is in good condition but has yellowed in some areas more than others. Also please note there is a small crack on the handset which appears to have been glued previously (see close-up photo).