Found this in a box of mixed parts and tools from an aviation workshop - they used to service Collins 618T HF radios, amongst others. Why would they haveengraved matching serial numbers? Critical component? The parts were partly rusted together but separated quite easily with a dose of releasing fluid. I think it got droppped into box accidently, as it didn't match anything else there. Is it a fly press tool/die of some sort? Best wishes, Tom G4KWL.