From the Tiffany's own press:
https://press.tiffany.com/the-collections/return-to-tiffany/ there are three mentions of 14k gold, so in the 60s/70s or earlier versions there might have been...
Hi everyone!
Has Tiffany & Co. only made 18k gold jewelry throughout all of time? I have seen some vintage Tiffany pieces stamped 14k. Does this mean they are fake?
according to Tiffany's own press (on their website describing Return to Tiffany collection) below, there are 3 mentions of 14k gold. So around the 70s there seem to have been some 14k products.
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A 1966 Tiffany advertisement showcased a heart-shaped Return to Tiffany® tag in 14k yellow gold, priced at $11 and hailed as the perfect Valentine’s Day present. A year later, in 1967, Tiffany debuted an oval Return to Tiffany® tag, also in 14k yellow gold, for $9. By 1969, Tiffany advertised a heart-shaped tag—still featuring the registered code number—on a keychain priced at $48, reminiscent of the modern chain bracelets featuring the key tag that Tiffany later introduced in the 1990s.
Over time, new takes on the familiar motif captivated the world with each new iteration. In 1980, Tiffany debuted the first jewelry design incorporating a Return to Tiffany® tag, a 14k yellow gold heart-shaped pendant on a box chain necklace. During the 1980s, Tiffany continued to offer the Return to Tiffany® tag on a screwball key ring.
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