From the estate of author, fishing guru, and winner of the Buz Buszek award, Andre Puyans:
For sale here is a Thompson No. 500 fly reel - made in California in the late 1940's. Diameter of is 3 3/8". Similar in style and performance to the classic Hardy Perfect. The reel is in excellent condition with the majority of its wonderful black finish remaining. Circular line guard and full-length smooth brass reel foot. The No. 500 was built to handle 6/7/8 weight lines. This drag system was unmatched in the American market back in the 50's. This is ultimate steelhead and light salmon reel for single handed rods.
From Dan Homel's book, Antique Fly Reels, A History and Value Guide, "The drag incorporates a separate brake shoe for tension and pawl for click, both mounted upon lever arms fitted to opposite sides of a brake drum. The brake drum is provided with a smooth surface to accommodate the shoe and a toothed area or ratchet for the click pawl. Overall tension can be adjusted in various combinations between the pawl and brake shoe by means of two individual knobs which each drive a spring loaded stem against their respective lever arm. A recessed roller cage houses loosely fitted ball bearings to ease the entire rotation process."