The 669 was the forunner of the 6906. Since it is discontinued parts will be kind of hard to get. But, if you don't plan on shooting 20,000 rounds out of it, it should do fine.
Ok, now with the gun TOTALY unloaded and all ammo in another room (and the gun pointed at a safe backstop like the fireplace) do the following:
With the magazine out, press the trigger to see if the magazine safety is there. If the hammer cocks and drops, then someone took the safety out!
Make sure when you take the magazine out and cock the gun (might have to put the mag IN the gun to cock it due to the magazine safety) shake the gun and see how much it rattles. If the slide to frame fit is not good and there is lots of leaway, well it's been shot alot.
Check to see if the hammer drops from the cocked position if you push on it with your thumb (and if so, the sear is bad so bye bye.)
Check the hammer drop lever for any cracks where they have used the lever excessivly and the hammer cracked the safety right in the middle (you should be able to see this from the back, plus the safety on the left side would be able to fall out.)
Check to see if there is any play in the barrel-to-slide. With the slide in battery push on the barrel, if it drops a bit down, then it's worn. Put a pencil in the barrel and see if the barrel wiggles at the muzzle. If so, the barrel is worn alot!
Put the pencil back in the barrel, point it at the cealing, and 'fire' it. If the pencil does not reach at least a few feet striat up past the muzzle end, then the hammer spring is weak or firing pin broke.
Make sure all mags hold open the slide when racked to the rear when inserted.
Check each magazine to make sure it was a REAL Smith&Wesson mag. Aftermarket mags are a source of much greef
Make sure the sights are in solid. No wiggle of the front or rear sight.
Make sure the grips are in good condition. No cracks or dents! The 669 grips are not put on like the 6906, so do look!
Now if it's in fine tight condition, and the price is right, then if you want it, get it. But, remember that it is just as thick as a Glock, if not more. So if it cost as much as a Glock, well I'd just get the Glock!
Deaf