phone connectors, these can be vary similar to other connectors in electronic boards. there are many different metal combinations used in electrical/electronic industry
they do plate gold on phosphor bronze also, either of these you should be able to recover the gold. although it is a little more difficult than from a copper/nickel plated gold.
iron or tin do complicate thins a little more, but electronic refining is more complicated to refine.
kovar is Iron, nickel,cobalt, maybe minute amount carbon silicone magnesium or similar complex alloy .
phosphor bronze is copper with 3% to 10%tin,1% phosphorous or similar complex alloy.
Iron or nickel can be magnetic
if you dissolve these they wont be kovar, or phosphor bronze,any more, as this is a name for the alloy of metals (like brass)and the expense may be in making the metal & not in its contents.