I have a Leader 2316 FM stereo generator I auctioned-in some years ago. It does produce all the stereo signals with L and R external inputs. It looks very much like the Panasonic or National units, and of course no service manual either.
When I wanted to use it for alignment of an FM tuner I had some doubts as to the precision of levels. In turn I configures the 8645A to produce the same signals so I could compare them, and in the end I only used the Leader for final checks and listening to something else than sinusoidal sounds ;-)
cheers
Martin
Martin