Is there ANY way to sell some industrial valves for more than scrap value without having paperwork?

Have you tried Craigslist or Ebay?

Without full records they have only scrap value, cannot be trusted without knowing the full history & useage

Figure out what their intended use was. Then find out who a valid group of potential users might be in your area. Then make sure that they are aware that you have these, and that you would happily part with them if you could get anything more than their scrap value. Maybe at some point they will be desperate enough to ignore what @nadanormal said, and tap your supply.