The abbrevation DBT stands for Denis Bertrand Trois Ponts (amorcée).

Length: 106mm , diameter: 50mm.
Weight: 645gram, including a 60gram TNT mixture.
It has an internal fuze with a fixed delay of 12 seconds, ignited when launched.
The body has a steel base plug, the fuze is aluminium.

This grenade got fired with the use of a special smooth-bore weapon, the "Lance-Grenades DBT".
In ww2, the German designation for this weapon was 5cm GrW 201 (b).
With this launcher, the grenade could be fired over a distance of 100m to 585m.

Photo right © Francesco Di Fraia.
Photo below © Siegfreid.