Interesting... I was reading online about the history of BMX and ran across a post by Cash Matthews who from what I understand is a member of the BMX Hall of Fame. He had this to say about the Mattel bikes.
"1962 Mattel introduces the Mattell Bronco and Stallion bicycles. These bikes had full suspension on the rear amplified by a swing arm apparatus on the backside of the head tube. They had knobby tires and a mounting place for a "Varoom" plastic engine that was controlled by a throttle piece. These bikes looked and sounded like real motor cycles. Unfortunately, BMX has not recognized this as the first production bmx bike, but it was a straight tube bike that pre dates webco by 12 years. If we are truly documenting history here, this bike must be given its proper place."