It could be before 1985, I don’t recognise any of those numbers as a date code. Hotpoint & Creda merged around 1989 when the Hotpoint date code system was used on Creda products.
Only knobs shown on Partfinder for a Creda 42107 hob (Brown) are 6225079 for the rear three and 6225150 for the one at the front of the hob.