For sale is a 1990s Mountainsmith Crestone II in great working condition. I picked up this pack last fall to use for a job, and no longer need it. It's not lightweight, but it'll stand up to being tossed in trucks, dropped, scraped, hauled, sat on, whatever. Manufacturer's claimed capacity is 5696 cubic inches, or roughly 93 liters. I carried 50-60 pounds in it. The brain of the pack detaches for use as a fanny pack, including its own full-width (but not padded) waistbelt. All zippers, drawstrings, etc. still work great. Some of the sizing adjustments may be a bit stiff. (I was just about the same height as the person I bought it from, so they just haven't been moved in a while.) One of the shoulder straps has been mended with a little bit of hand-stitching where a seam started to open up. The foam inside the back padding is starting to degrade and shed, but I haven't noticed a drop in comfort.
Asking $50. Local pickup in the Bay Area preferred; otherwise, buyer pays cost of shipping.