This has been my general rule of thumb over the years for vintage license plates: Don't pay more than $1 each, and sell them for a quick $5.
Or use them to decorate a multitude of items.
So now the new general rule of thumb is: Don't pay more than $1 each, sell the ones after 1970 for $5 each. Research others, probably put them on ebay.
Linking up with:
Funky Junk Interiors