No 81 Mk I Fuze Diagram during World War I

Diagram of British No. 81 Mark I Time & Percussion fuze, Naval service, World War I era.
It is an improvement on Mk 80 fuze. The lighting pellet is to the side rather than central, to avoid risk of accidental firing caused by heavy knocks. This also allows for a recess in the nut to facilitate use of an automatic fuze setter.
Body is of aluminium, threaded for 2-inch fuze gauge.
Burn time is 30 seconds at rest.
Intended for long-range shrapnel fire with the following guns :

BL 13.5 inch Mk V
BL 12 inch
BL 9.2 inch
BL 7.5 inch (except Mk III & Mk IV)
BL 6 inch
BL 4 inch Mk VII - VIII
QF 4 inch Mk IV - V
QF 12 pounder 18 cwt
QF 12 pounder 4 cwt