"PACK-MULE trail scooter has a specially designed conversion unit that changes it from a regular two-wheeled type to a half-track drive vehicle, as shown above. The drive permits controlled speeds from 1 to 32 mph in sand, snow, shale, and over rough terrain, it is claimed. Available with 3, 4, or 6-hp engine, climbs 45 degree grade. Drive-X Co., Madrid, Iowa." 1