WOW you know I forgot about that one. Thanks for the reminder. We used to break those thermomters open for the Mercury to do that with. Got caught doing that too and ouch. And as to age, we should all try to remember that GDJMSP knows so much about coins since he invented them a long, long time ago.
Essentially all the silver "collector coins" on display at shows in the 1960s were bright white. If you had the baking soda concession back then you would be rich today.