It's probably missing an auxiliary handle.
Pneumatic powered chain saws were built mainly for use in old, smaller underground mines [before the days of trackless mining with the diesel LHD loaders, drilling jumbos and underground haul trucks that are used now].
Reticulated compressed air at ~90-100psig was used throughout these mines as a power supply. These saws could also be used underwater if necessary. These mines used a lot of timber for ground support, hence the need for chain saws.
Underground plant items such as rock drills, 'boggers' that loaded the blasted rock into hand-propelled 'trucks', winches, and ventilation fans were all air-powered in these mines.
Lighting, and shaft cage winder/s if they were positioned below the surface, was often the only use of electricity underground then, and even then it was restricted to the vicinity of the [usually vertical] mine haulage shaft. Electric pumps for dewatering, positioned in the sump at the foot of the shaft, were also used in these mines, in more recent times.
