The Model 10 is a "K" frame (medium) gun. The -7 means it is a series 7. They stamp a progressively higher series number with each model up-date. Not sure about the E6 stamp. Nice guns. 20 years ago, when most police departments switched to the new wonder 9's, lots of Smith K frames were flooding the market as police turn-ins, and were selling dirt cheap. Not any more though. Prices have climbed quite a bit on the classic Smiths.
Larry