The1897 patent  for this airbrush lists Wold as the inventor and it is assigned to (owned by) his employer Thayer & Chandler. Olaus Wold was the great innovator in the early years of the airbrush. This is the first one that has the trigger assembly isolated from the paint. In previous airbrushes the trigger sat in the middle of the paint reservoir . A mess to clean up and it made color changes difficult and tedious. It also features an easily removable needle that didn't require any tools as on earlier models. A very rare Thayer & Chandler and this is the only one known to me.

An 1897 Wold/Thayer & Chandler double action airbrush that uses a sliding trigger. To get air you rock the trigger forward and to get paint you slide the trigger back.