Not the first time StH has got things wrong (319 was for ailerons,) and Spitfire mods had a different series of numbers from Seafires. Seafire 697 was “To introduce a slotted type cap for oil filter door.”
Edgar

That’s a disappointment – it’s a huge volume of information, which apparently now can’t be trusted. Oh well…
Having the same numbers for different mods on essentially the same aircraft must have been confusing for the erks!