distributor solenoid purpose?

no its most definatly electronic ignition, I'm very familure with small blocks and slants but this is the first big block I have had the chance to do much to, I knew slant distributors only fit slants but wasen't sure fitment from small to big block, it looks identical

wire definatly goes directly to the advance canister, but the van isn't lean burn or have any emissions stuff on it. It also has the normal vacuum line to the advance as well as the wire, I have seen points distributors this way but never electronic ones

rock auto lists it as "W SOLENOID OPERATED VACUUM ADVANCE UNIT"

well it has to be an emissions thing... it must open or close the adv canister even if the vacuum isn't there... get more timing in under certain conditions...