I'm in the midst of tyding up old papers and came across the booklet and receipt for my Philips Rotary. July 1984 Philishave HP1605 mains powered I used to have one of those little sharpening gadgets from a previous shaver which was basically a bit of emery in a cylinder. So I've sharpened the blades on a stone and more recently tried the diamond credit card sharpener, very gently.
It's not brilliant now so I have a 7 'o' clock shadow unless I spend ages. I've had to pull a couple of blades out as they were catching.
I do have a later battery Philishave which only gets used when I'm travelling which is occasional at best and zero at the moment. It does give a smarter shave than the old one.