First off, no such thing as a nickel 66. All model 66's are stainless. The 66 is a stainless model 19. The model 19 can be had in blue or nickel.
As to value, that's a little tricky. Commemorative guns should be NIB to realize their full added value. If it's just a shooter, than it's basically worth what any shooter is worth. To the average person, a commemorative is worth little more than a regular gun in similar condition. Now, to a serious S&W collector looking to complete a collection - or someone that has a personal tie/relationship to the commemorative ( in this case to the Lynchburg, Virginia police department), the gun will be worth more.
Me personally the Lynchburg, Virginia police department commemorative is worth no more than a regular 66, maybe even less. I'd rather have the standard 66-2 in my safe than one that says Lynchburg, Virginia police department on it.
Engraving? Well that's a bit tricky as well. I have no knowledge of this engraver. Might be good, might be bad. Some people prefer factory engraving. Hand engraving can cost way more than the gun itself. Does it add value - usually - maybe - it depends. How good is the engraving? What style and type and coverage? What is the current condition of the engraving? What is the condition of the engraved gun? Just like commemoratives, to get the full value of the engraving the gun should be NIB.
Commemorative guns are a niche product. Engraved guns are a niche product. Non-factory engraved commemorative guns are really a niche product. A serious S&W collector might not want a non-factory engraved commemorative.
So what's it worth? Hell if I know.