eluu: SCSW indicates that the 61-3 was introduced in 1971 at S/N B40001, so you might want to check the numbers again. If correct, it wouldn't be the first time that Smith did something out of order or that the book needed a bit of tweaking. Still, the information given in the book is very definitive with regard to the Model 61 "dash" variations and their respective S/N ranges, which isn't always the case with many other models. If it's actually a 61-2, then the production date would be 1970 and the S/N would be in the right range.
The book lists the value, in excellent condition, at $250, but it's now more than 3 years out-of-date, so perhaps another $50 or so might be closer.