I have a M&P Shield 9mm that a friend wants to buy. The s/n is HPT6xxx. How do I find what year it was manufactured and what price it would be worth. Has truglo sights. Any ideas?

You can buy a new base model for $299. So it would have to an awe cul low price for me to justify buying a used one.

If the owner still has the box and Test Fire Case envelope, the Date of the Test Fire (on the envelope) will be within a week of manufacture.
The Date Code itself would be on the Box's Label.
If it was made before Mid 2013, the manufacture code would be 4 digits, with the 1st digit being either a 2 (indicating 2012) or a 3 (indicating 2013). After that, the manufacture code would be a simple MMDDYY 6-Digit code.

Of course... If you buddy either calls, or emails S&W CS and gives them the full #, they will tell him.

But as mentioned above... With the price of a NEW Shield being in the $300s, the price of the used one would have to be a REAL deal.