Another weirdo here, just how many hot-rod crawler tractors do you see out there? I guess Matchbox were just trying to upgrade their core products and make them more contemporary. They always had a bulldozer in the range, and as all the cars were being tarted up to compete with Hot Wheels, so why not do a hot-rod bulldozer? However Matchbox being Matchbox they retained the authentic caterpillar crawlers where Mattel would have made them dummies with hidden wheels underneath so they could still use the tracks.
Big Bull, 12e, was released into the community in 1975 and stayed there until 1979. The slightly harder to find versions have yellow rollers and the least common have black rollers, orange rollers are most common, but none attract much of a premium.
