Surprisingly, this is old news for anyone who is an avid follower of SoloDallas. http://www.solodallas.com/the-vintage-marshall-guide/ Anyway, on Fil's website, JaiminhoPagina made an article explaining all the different models of vintage marshalls and the company's history with them. In said article, he reveals several tasty tidbits about the amp Slash used to record Appetite for Destruction. It doesn't disclose the current wherabouts though. You'll have to search a bit to find the correct section, but it's there.