In the beginning of the first chapter of The Adventures of Tom Sawyer by Mark Twain I read:
The old lady pulled her spectacles down and looked over them about the room; then she put them up and looked out under them. She seldom or never looked through them for so small a thing as a boy; they were her state pair, the pride of her heart, and were built for "style," not service -- she could have seen through a pair of stove-lids just as well.
So what does state pair exactly mean and what is the etymology of this collocation?