For many years the GW design studio played a game called Confrontation that was the precursor to Necromunda. There were many White Dwarf Scenarios and rule sets published before the final boxed version of Necromunda was released.
There were two different sets of miniatures designed for Confrontation/Necromunda. The more common one was the Marauder set designed by Trish and Aly Morrison, released at Games Day US 1991 and somewhat available for a short while after that. The rarer ones are the Citadel ones, designers unknown (Mark Copplestone?), but the leaders are by Jes Goodwin.
The Marauder gangs are all marked Marauder and coded MM110, but the leaders are marked GW91.
Marauder Nomad Gang
Marauder Psyker Gang
Marauder Scavvy Gang
Marauder Tech Gang
Marauder Venator Gang