Hi, you have an early version of a reel that EVH made and sold for a long time...very popular model 621. Yours has the push-button clicker, which they stopped using in 1922. You operate the free spool by pushing (rotating) the rim control on the face plate side forward, which pulls the gear away from the spool (shown here, in gear):
Note that the mechanism often gets gunked up by old grease and may or may not act as intended. If you don't get any free spool by turning that knob, the reel needs an overhaul.
The rim control on the back plate operates a "soft drag" that acts on an adjustable saw-tooth gear on the back side of the pool. The tension on that gear can be adjusted, but you have to remove the back plate to do it. When engaged, you can see how the arm controlled by the rim control will apply resistance on an outgoing line:
