One thing that has puzzled me, and I haven't come across an answer, is why the Chevy S-10 Blazers and GMC S-15 Jimmys are just labeled Blazer and Jimmy on the board. The Chevy used the S-10 prefix from 1983-1994, and the GMC used the S-15 prefix from 1983-1991 (when GMC renamed the larger model Yukon). These models were marketed with the prefixes, as shown on these brochures:

http://oldcarbrochures.org/NA/GM-Trucks-and-Vans/1985_Trucks_and_Vans/1985-Chevy-Trucks/1985-Chevy-Trucks-07
http://oldcarbrochures.org/NA/GM-Trucks-and-Vans/1985_Trucks_and_Vans/1985-GMC-Light---Medium-Duty-Trucks-Brochure/1985-GMC-Light-and-Medium-Duty-Trucks-09
http://oldcarbrochures.org/NA/GM-Trucks-and-Vans/1985_Trucks_and_Vans/1985-GMC-Trucks/1985-GMC-Truck-11
http://oldcarbrochures.org/NA/GM-Trucks-and-Vans/1986_Trucks_and_Vans/1986-Chevy-Truck-Facts/1986-Chevy-Facts-037
http://oldcarbrochures.org/NA/GM-Trucks-and-Vans/1988-GM-Trucks-and-Vans/1988-Chevrolet-Commercials-Brochure/1988-Chevrolet-Commercials-08
http://oldcarbrochures.org/NA/GM-Trucks-and-Vans/1989-GM-Trucks-and-Vans/1989-GMC-S-15-Jimmy-Brochure
http://oldcarbrochures.org/NA/GM-Trucks-and-Vans/1990-GM-Trucks-and-Vans/1990-Chevy-Trucks-Volume-1/1990-Chevy-Trucks-V1-55
http://oldcarbrochures.org/NA/GM-Trucks-and-Vans/1991-Trucks-and-Vans/1991-Chevy-Trucks-Full-Line-Brochure/1991-Chevy-Trucks-35
http://oldcarbrochures.org/NA/GM-Trucks-and-Vans/1991-Trucks-and-Vans/1991-GMC-Trucks-Foldout/1991-GMC-Trucks-01

I know the 2nd generation models were just Blazer and Jimmy, but the first definitely used the prefixes. So I'm curious if there is a reason for this and any opinions.