The M142 Firing Device can be designed to function in the following modes:

Pressure (11 kilograms or more).
Pressure release (between 2 and 67 kilograms).
Tension (3 kilograms or more).
Tension release.

All photos © Scott Lynch.
The same device was used in Australia under the name F1A1.

Case: Plastic.
Color: Olive-drab.
Diameter: 190.5 millimeters.
Length: 571.5 millimeters.
Internal action: Spring-driver striker.
Safeties: Positive safety pin, square-head pivot pin, round-head pivot pin, and alternative safety-pin hole.
Accessories: Nail and screw fasteners, coupling assembly, tension-release attachment, 15-meter spool of trip wire, and vinyl instruction sheet.
Packaging: Round, metal can containing FD with accessories.

Early and Late issue

Instruction leaflet :

Metal can containing 14 devices