This is an original Finnish m/40 field spade carrier.
The longer D-handled m/40 Field spades were meant to replace the so called m/18 Tsarist type field spades during the war, but it seems they were only started being introduced later in the war.
The carrier has a large steel hook, which holds the spade through a hole on the blade. The hook is closed with a spring clip. The carrier is hung from the belt with a belt loop. The handle of the spade is meant to be tucked under the belt to keep the spade from swaying around.
Some of the carriers have SA and / or P stamps.
Price is for one.