Working off memory here again at work (when I should be working yea yea), so if I make an errors please someone jump in.
By all rights, a Württembergisches officer's Pickelhaube with silver fittings, but with flat brass chinscales and brass rosettes, would be from Grenadier-Regt. Königin Olga Nr.119 or Grenadier-Regt. König Karl Nr.123.
With silver rosettes, but also with flat brass chinscales it would be from Württembergisches Pionier-Batl. Nr.13.
With silver rosettes, but with rounded brass chinscales it would be from Dragoner-Regt. Königin Olga Nr.25
For an M15, if the chinscales are brass, it would make sense that so are the rosettes as they are faux and part of the mount. No?