The following document details the official Philips model numbers for the period 1970-1981. My thanks go to Barry (Red to black) and Stan (valveman49) for this valuable information:
Philips Model Identification 1970-81 NB: This link downloads a .PDF document.
NB: Some sources question the ‘total accuracy’ of this information (please bear this in mind). It will however be a very good guide.