This type of pre-air cleaner was very common on farm tractors and bulldozers in the 30's and 40's. Any equipment that worked in a high dust/high particulate environment. Everything from tiny Farmalls to big Cats.

.

Again just trying to share information here, NOT trying to criticize a great model in any way, shape or form.
I learned about this item as part of my research while building my own Mirror Models D7 dozer. That is a standard small glass Ball Canning Jar with the perferated lid attached to the air filter. The idea was that the driver could keep an eye on the glass jar and when it got full, unscrew it and dump the contents.