This defensive grenade was made of cast-iron and was produced in Barcelona in the autumn of 1936.
The base is shut and the top is threaded to accept the fuze mechanism, which was called "B-3".
This mechanism was a copy of the Polish wz. Gr.31 fuze or French billant fuze. The difference with the original polish and french fuze was the diameter of the threads.

Grenades were manufactured by several companies, therefore different markings are seen on these bodies.
Sometimes there are no markings at all.
Examples are "S", which was made by Sabadell and "CNT/4", which was Factory Nº4 of the CNT militia.

Length without fuze : 75-80 mm (6 rows of fragments)
Length without fuze : 105 mm (8 rows of fragments)
Diameter : 40-45mm the "6 rows"
Diameter : 45 the "8 rows"
Filling : Nitrate

Information provided by Dani.

Photo right and below © R. Seyfrid.
( 110mm high, 43mm diameter)