Heater line lever?

I have these heater lines that came attached to an la 360 that I was told came out of a 74 duster. The lines have a cap, I am guessing this is some sort of bleeder but I am not positive. They also have this strange fitting that runs between the two of them and has a lever on it. I can not figure out what this is, can someone please help? Thanks in advance.

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