The type 3 disruptor was a classification form for a specific type of directed energy weapon that could be identified by their blast pattern that were mainly used by the Klingons, the Breen, and the Romulans..
In 2370, weapons of this type were used in the attack on the Amargosa observatory, and upon the arrival of the away team from the USS Enterprise-D, Commander Worf was able to identify them as the cause of the damage to the space station, allowing Commander William T. Riker to narrow down the choices of who attacked. They then happened upon a Romulan corpse, and were able to ultimately confirm who was responsible. (Star Trek Generations)