Per the Woodwind and Brasswind (presumably lifted from Yamaha literature). While the saxophone isn't addressed, the effect of plating on clarinet keys and posts didn't just nibble at the edges of a discernable difference, didn't merely add warmth to the tone, but actually made "a dramatic difference".
Boy have I (many of us) been wrong on this one.
Case closed, no further room for discussion. On to precious stone key touches...
Yamaha YCL-CSG Series Professional Bb Clarinet
What is HAMILTON PLATING?
Hamilton plating is an alloy of gold and nickel. It's extremely resistant to wear and discoloration, and delivers a powerful tone with excellent projection. On the CSGH instruments, the Hamilton Plating is actually not only on the keys, but on the posts as well. In artist testing, it was shown to be a dramatic difference between instruments that had just Hamilton plated keys and Hamilton plated keys and posts.
lest you think I'm making it up: