Hi Q T,
Welcome to the forum!
The "dash" number, 10- (dash) 7, indicates an engineering change, in this case the gas ring on the standard barrel model 10 was moved from the yoke to the cylinder. The 10-7 series started in 1977. The same change in the heavy barreld model 10 became the 10-8 series, same year.
Recheck your serial number. It should be three letters and four numerals. Your AD7 is probably ADT 3xxx. The ADT 3000 series stared in Jan 1984 and ran for several months.
K22 is right, the pinned barrel was eliminated in 1982 but S&W doesn't throw stuff away and unused pinned barrels can show up long after their "discontinued" date. During periods of transition from one change to another parts sometimes overlap. In the case of magnum guns, there are cases of pinned barrels appearing with non-recessed cylinders and vice versa. Just a case of not wasting the inventory on hand.
Look under the extractor rod to see if there is an "N" on the flat part of the barrel; if so it was factory plated.
Also check the back of the cylinder for an "N".
The model 10 was introduced in 1899 and is still being made today...millions have been made...so value is very subjective. An average starting price for one in decent condition is around $400 but condition, age and many other factors can be a plus or minus. Nickel finish, if factory original , can be a plus. Looks like your grips have been lacquered
.
Nice gun and a good shooter. I've owned and shot model 10's for over 50 years.
Two model 10's and a stainless model 64 - just a model 10 in stainless steel
P. S. : Plate looks delish...makes me hungry
