The Model AB "Pioneer", from what I understand, was the updated version of I.E.L.'s first one man chainsaw model "Beaver" which was also the first one man gas powered chainsaw made.  The saw is a pretty simple design with everything in line. A nice show piece on any shelf. These real early design saws seem to all take advantage of a gear drive or in this saw a roller chain reduction drive to help add torque because they ran on lower RPM's compared to modern saws. Example:  I.E.L. AB "Poineer" 4,000 RPMs (1948-50) Stihl 046 13,500 RPM's (introduced in 1995).