1989
This article appeared in the March 1989 Bicycle Guide magazine. It sure appears to be the later Boulder design but I am not sure if it is the same designer or not?
1991 September BIKE magazine (German) review:
March and October 1991 bike ads:
November 1991 prototype with Action Tec and Rock Shox suspension:
1992 January Boulder brake press release:
1993 September Boulder Defiant Ad:
Former Boulder designer introduces his own line of bikes in October 1993: