I think I may have a trace of rust...

[swee'pea99]

That looks a lot better - I wouldn't expect anyone to buy the zinc primer just for a one-off. I've used it (on the underside of a steel fuel tank on my car) and it certainly works.
Does the seatpin on your bike move? I'd take the opportunity of removing it and greasing if you haven't already done so.
p.s. I saw a bike frame damaged when someone undid the allen key (like yours above?) because they didn't realise one side had a 'tag' into a slot (if that makes sense), and they took an allen key to the other side and turned, when they should have used an additional AK on the 'fixed' side.

Thanks for the heads up. I did know as 'it 'appens, but a kind thought, and much appreciated. Sadly I have to report that I went to considerable efforts to shift the seat post, some years back, with zero success. I'm kind of resigned to it now. Long as it sees me out, then someone else with the same size legs can take it over 😀