Nos?????

I'm bidding on a water neck elbow on eBay that was listed as

1961 PLYMOUTH VALIANT 1962 1963 VALIANT PLYMOUTH DODGE
NOS WATER NECK ELBOW PART # 2121 524


I asked the guy if that was aluminum or cast and he says it is aluminum. If it is aluminum, wouldn't that make it an aftermarket replacement piece and not NOS?

Most, if not all Mopar t-stat housing were aluminum, not cast iron. The housing on one of my Valiants has the numbers 2121 524 on one line, the next line is 09104. Also on the housing is "made in canada", and the Chrysler logo. See it the picture shows the logo.