This strange device is a rare ww2 British training S-mine.
It has a
No.2 British pressure switch cast into the concrete body.
Its not a training device to disarm an S-mine, but for stepping on to make the person activating it aware.
The original finish is olive green, it is unknown if the mine carried any paint markings.

Photo right and below © Pat.
The mine shown was recovered near Caen, France.

The top part is made of brass and the screws, filler and det plugs are soldered in place and cannot be removed.
On top of the mine is a threaded nut where a special type of igniter was fitted, this is sealed with a cork shipping plug.
The threaded nut is soldered in place and the thread inside the nut is much corser than any German igniter, so German igniters will not fit.
On the inside, the top of the mine it is marked with a very small manufacturers stamp. It was a proper manufactured item and not improvised by a unit.
The base of the mine is made of a kind of concrete material similar to the hard dark concrete block you find today.
The pressure switch-part that protrudes from the side of the mine has an unscrewable cap holder that can be reloaded.

Chris made this photo (on the right) at the Imperial War Museum.
The grey paint and the white stenciling are not correct.

Photos right and below © Chris