In the Le Grand size the Solitaire models were made above all as fountain pens. Rollerballs existed too, but only until 2002 and not in every Solitaire finish; they are documented for Sterling Silver and for Vermeil among others. Ballpoints and propelling pencils, by contrast, were never offered in this size. A gold-coloured Solitaire rollerball in Le Grand size is therefore perfectly possible, a ballpoint of the same size is not, and an offer of one should give a buyer pause.
One case remains unresolved, that of the Stainless Steel range: when the series was first presented in the trade press, a rollerball in Le Grand size was pictured, yet it appears in none of the later catalogues and hardly anyone has ever seen one. It was presumably planned but never went into production. Before buying, then, it is worth checking size and finish against period catalogues and measuring the length, because the difference between Classique and Le Grand is easily missed in photographs that offer nothing to judge the scale by.