its from the web not my comment
Nakamichi plugs made of IRON
I discovered that Nakamichi banana plugs and spade terminals are gold plated iron, NOT "pure copper" as advertised. Note that it appears that Nakamichiplug.com is NOT associated Nakamichi.com; I have no issues with Nakamichi (the real one) gear. I have seen several postings on this forum and others about using Nakamichi banana plugs and other connectors, and wanted to let folks know that they are an overpriced piece of gold plated iron. Hey, they look nice, and the moderate price would make one think that they're getting a good deal. Nope.
Discovered by breaking a tip on a spade plug trying to get it to fit an 8mm post; copper doesn't snap like that and upon magnification is definitely not copper by looks. Filed down that piece, and sample filings on other pieces and also some banana plugs, discovered all were a gold plating on copper plating on soft iron. Finally verified it by dropping it in some hydrochloric acid, and as expected the iron reacted (slowly). (Don't have any nitric acid to test with which is very reactive with copper but not as much with iron.)