The No.13 "Pitcher" grenade was made of a prefragmented cast iron body.
A charge was inserted from the top and fixed with tar.
It had a pull-ribbon under the safetycap which was treated with red phosphor and ran through a matchhead compound.
Together with the No.14 (similar, heavier) these were the most dangerous of them all.
A lot of these grenades exploded immediately when the ribbon was pulled.

Length 110mm, width 51mm.
Weight 510gram including 113gram ammonal.

The grenade on the photo below carries the markings "ROBURITE & AMMONAL LTD No14 4/1915"on the safety cap.

Photo © Paul Spence.

This shows the "drill" version, painted white.