Found in a mine in the Rand Mining District, in the Mojave Desert, California. They are covered in candle wax from the candle the miner was using to light the tunnel he was working in. They were found with an old paper bag with the name of a mercantile store, W.C. Wilson & Co., which operated between 1895 and 1898 in the town or Randsburg. There was also a gunny sack with the initials APK and "Randsburg" marked on it. APK is through to be Adam P. Kuffel, a partner in the mercantile store.
Lot 201, the "value" version of the 501XX, was made from 9 oz. Amoskeag denim
More about: W.C. Wilson & Co.
Update: Ended at $36,099, congrats vintboy1!
Also: From a letter sent to Levi Strauss by Jacob Davis, a Nevada tailor employed by Strauss in the early 1870s: "The secratt of them Pants is the Rivits that I put in those Pockots... I wish to make you a Proposition cap that you should take out the Pantent in my name as I am the inventor of it."