The model 10 has been in production since 1899, know then as the .38 Military & Police. Model number were not assigned until 1957. They are the quintessential military and law enforcement gun of a bygone era. The guns as you have already noted, are chamber to fire the .38 S&W Special; are built on the "K" or medium frame. S&W has produced many fine guns in diferent frame sizes each to fit a particuliar nitch or requirement. The "K" frame is a very well balanced carryable gun. The -6 indicates the 6th engineering change and was produced from 1962 untill 1977. If the serial number has a "D" in it that would make it post 1967. The S.N. can be found on the bottom of the grip frame and with it we can thighten up on that date some. They are, as you have also noted, an excellent choice in weaponary.