Thanks for that!! OK, so I'm sure I had the s0 (with the Hulk Green band) and then an s2, but never an s1. Then an s3, s4, s5, and now s6.I can't speak for the Rose Gold, but the S0 launched in May '15. In September '16 the big news was S2 with GPS and water resist (I think).
Less well publicised was that the original was quietly replaced by a new model that was logically the S1, with basically the same specs but faster. That became known as the S1 (I don't recall if that was an official Apple naming, but I think it was) and the pre- Sep '16 models the S0.