Fort Missoula, for nearly a century a military fort, is now a National Historic Place and park. In the park are a few of the pre 20th century buildings from the original 1877 fort and many buildings from the early 1900s. They have an eclectic collection of large artefacts, including machinery and tractors, a lookout tower, railroad engine and cars, a tipi burner, the old Drummond, MT RR station, an old school and an old mission, artillery and a historical museum. It's a great place to spend an afternoon or a whole day.
This compressor is on display in the machinery display area at the southwest corner of the park.
Ingersoll Rand has been a leader in air compressor manufacture for well over a century. These self contained compressors were introduced in the early 20th century and been very popular ever since. The Gyro Flo were, I believe, introduced in the 1950s. The 315 produced compressed air at a rate of, you guessed it, 315 CFM. These used a diesel engine, manufacturer unknown.