Abstract: A lottery card comprising a given number of fields, arranged in a successive order. Each field is divided into a given number of frames. At least one of the frames of every field contains a mark. All marks are related to each other according to a successive order, and are concealed by being coated with a removable coating.

Abstract: A rotary engine includes a housing defining an annular space in which two block-like pistons, each having a first side, are arranged for orbiting movement in opposite directions and so as to come into a face-to-face engaging state across the width of the annular space, with their first sides directed toward each other, at each of two opposite locations in the housing. At least one of the pistons has a concavity at its first side so that when the pistons are in their face-to-face engaging state, a sealed chamber is defined between them. An arrangement of pins connected with the pistons and riding in grooves provided in the housing enables the pistons to rotate as a unit about an axis of the unit by 180.degree. in one sense while engaged at either of the said locations and then to pivot individually by 180.degree. in the opposite sense after separating and preparatory to approaching each other for engagement at the other location.