Three-handed chess: Self's variant

In 1894, Hency J. Self proposed this chess variant for three players in his book (or booklet) New and Improved Game of Chess for Three Players. The game is mentioned in Pritchard's Encyclopedia of Chess Variants.

Rules

The game is played by three players. The following board and opening setup is used.

The first player to deliver a mate can claim back any piece lost. The piece is placed on its original square, or, if this square is occupied, on the nearest free square, with preference to a square on the board edge, when there is a choice.

The winner of the game is the player who mates both opponents.

From Pritchard's description, it is not entirely clear how the rules are precisely; one could for instance leave the pieces of the first mated player on the board to be taken, or remove them all when the player is mated.