The Rep pair of Spikes I tried had SS printed on them (Matte Black Combo) and I figured it was a marking for prototypes and ealry production models. When he brought the first Gascan in it was marked protoytpe or similar as well. Oh, he didn't know what it meant either.
It's kinda weird that only the European Spikes apear to have 'SS' on them. Hope there's not too many in the shops, cause it might shock some people that are too much into history.