Sounds right - my '71 Schwinn Continental has identical levers as well (in fact, that is where the example on the left came from).

Rabid Koala reports the same design as original from his '72 Paramount. I've seen the example on the left on machines dating from the late '70s and into the '80s. I gather it is safe to assume that the change happened sometime either in the mid to late '70s.

-Kurt