I acquired this poster stamp/cinderella recently. It's from the European Air Race of 1911.
It is listed in the Gardiner/Greiczek catalog as arc roulette. No mention of colored. G&G also list a second type where the rouletting/perforations are printed but not cut (false arc roulette)
It is listed in the Silombra catalog as "serration printed 11 and not cut" (Google translate), but the picture next to it shows a perforated stamp. It doesn't list a second type.
I have seen roulette in color before, but this stamp doesn't look like the arc roulette pictured in my "Fundamentals of Philately" by Williams. That indicates that it should be a series of scallops with sharp almost triangular points in between. These look more like flat perf tips. And they do measure out as perf 11. But I've never heard of "perf in color". Can anybody out there tell me what I'm looking at?