And yet, you can see the "Straƶ Miejska" logotype linked in my comment above, with a crown on the eagle, so post-December 31, 1989[0].
It may depend on the region (I was raised in the eastern Poland) but I also remember that in the primary school we used a different symbol for the letter "s". But only in hand-writing while any printed "s" looked like it does currently. I'm unable to find the UTF-8 character resembling the hand-written version.
> It represents the same sound in the Polish alphabet, remaining in active usage by some as an alternative for the letter Ż (called "Z with overdot").
> In Polish, the character Ƶ is used as an allographic variant of the letter ⟨Ż⟩ (called "Z with overdot") although once used in Old Polish.
Funnily, there's a counter-argument to "Straż Miejska" from article you linked, with "Straƶ Miejska" in another Wikipedia entry[1] :)
[0] https://en.wikipedia.org/wiki/Z_with_stroke
[1] https://en.wikipedia.org/wiki/File:Straz_plakietka.svg