No. Fountain pens of the Meisterstück Solitaire line were supplied throughout with two-tone 18-carat gold nibs, that is with the familiar interplay of a yellow-gold ground and rhodium-plated decoration. That holds for versions such as the Solitaire Carbon Steel and the Solitaire Doué Signum as well; single-tone platinum-plated nibs are not known on these models.
Single-tone, fully platinum-plated 18-carat nibs were used by Montblanc on other lines, among them Bohème models of 2004. Anyone finding such a nib on a Solitaire should therefore consider whether it was swapped at some later point. Changing a complete nib unit presents no technical difficulty on the Meisterstück models and is common enough after a repair; on a collector's piece, however, it detracts from originality and hence from the price achievable.