The deck shell is described in the Asti Manuscript, c. 1670-1730, p. 97 of the Pieper translation, as a method to hide livestock. This manuscript was translated in Gibecière, Vol.8 No.1, Winter 2013, p. 29-234.
A deck switch using a Card Case Shell was published by Stanley Collins in his trick “The Flying Sum and Divining Cards” in Will Goldston's The Magician Monthly, Vol. 9 No. 8, July 1913, p. 124. The shell is openly transferred from one deck to another in an off-beat moment. Also see Deck Switch with Shell.