I purchased a 639 today in nice shape. Price was probably a touch high, but in California that’s to be expected for “off roster” pistols. They don’t come up too often and I figured it would go well with my 659. Fixed sights, ambi safety, and square trigger guard. It’s a true 2nd Gen with the removable bushing and not a transitional 3906. Based on the serial number of TBTxxxx, I’d guess it’s from near the end of production. Can anyone confirm that?

Can't help with the serial number, but ambi safety and hooked (square) trigger guard are the hallmarks of the later production versions of the x39 and x59 pistols.

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VCDL, GOA, NRA

Yes, between that and my 1985 production 659 having a TAFxxxx serial I figured that the 639 I purchased was likely made in 1988 or later. When was the switch to 3rd Gen?

The 3rd gen pistols went into production in 1989.

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VCDL, GOA, NRA

No help with date (I’m away from my SCSW-4) but I will say that IMHO, the 639 was “pick of the litter” for all of the 39 series of S&Ws. It was my choice as the basis for my Franken-Smith build and I’ve never looked back. Up until a couple of years ago, orphan slides from 439s, 915s, etc were cheap and plentiful so I was able to get one to add classic Millett adjustable sights and another for a reflex optical. They’re kinda like an Erector Set… you can put together whatever pleases you.
The only drawback is getting original mags. The aftermarket versions are spotty at best.
Froggie

Called S&W CS this morning. My 639 was manufactured on June 18, 1988 which I’d imagine would make it one of the last 2nd Gen pistols made.

I would have to agree that June of 1988 is at the extreme end of 2nd Gen production.

You will find that nearly all of the very earliest 3rd Gens are clearly 2nd Gen top ends that are modified for 3rd Gens.

I’ve seen a few of the “transitional” pistols online but I’ve never seen one in person. The one I bought is not a transitional…it has no 3rd Gen features that would make it a transitional 3906.

I am fortunate to own two 3906’s and one of them definitely has an upgraded 2nd Gen slide.

This thread reminded me...still need to shoot my 539 and 559 pistols. They have been sitting in their respective boxes and never fired.

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No good deed goes unpunished.

That’s a beautiful pistol. Few finishes beat classic bluing.

IMHO, the two major differences between 2nd and 3rd Gen slides are the barrel bushing arrangements and the ability to change the front sight easily (on a dove tail.) I like the latter a lot and chose a 915 slide to mount my classic Millett adjustables, but then chose to use a 2nd Gen slide for my Reflex sight since the front sight doesn't matter. Then I just have to remember which barrel and bushing go together. Like I said, an Erector Set, just a big toy for a big boy!
Froggie

The June 1988 date fits for sure with last of 2nd Gen. The Model 639 was introduced May 24, 1982 and discontinued in 1988. SCSW 4th only shows 1987 TBC, TBD, TBL and 1988 shows TBC, TBF, TBL No TBT that I could see.

Mine does not have a triple alpha s/n, rather A 830417 and it shipped in June 1983 per Dr. Roy.

Mine came to me missing the ambi-safety right side lever and screw. I got hold of the lever, and a generous Member here on the Forum sent me a factory original Phillips head screw. The screw does seem to shoot loose and lever gets lost according to numerous other posts about the 639 so I have mine for originality, but screw and lever stay in the box when I go shoot this gun. I'm right handed so don't need the ambi lever anyway.

Love the gun. I'm sure you'll enjoy yours too.

Attached Images

	Mod 639 left side.jpg (60.4 KB, 29 views)
	Mod 639 right side.jpg (68.3 KB, 20 views)
	Mod 639 factory Phillips safety screw.jpg (67.1 KB, 21 views)
	Mod 639 mags -a.jpg (71.1 KB, 14 views)
	Mod 639 mags -d.jpg (100.0 KB, 16 views)

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Charlie B
SWCA#3083, SWHF#570

I absolutely agree that these are the major differences and the easiest way to spot a 2nd Gen slide.

The others I've observed are that 3rd Gen slides have ambi-decock levers and of the final design for the right side lever but also... the metal finish on the 2nd Gen slides and the lettering font are noticeably different.

Even the upgraded 2nd Gen slides used on early 3rd Gen pistols show a different metal finish (as if the 3rd Gens are bead blasted and the 2nd Gens are a dull polish that may not be bead blast, or certainly a different grade of blast) and the upgraded 2nd Gen slides use their old school lettering including the classic "four lines of information" that most of the 3rd Gen pistols did not use.

Obviously, I need to take comparison pictures of my two 3906's to detail these differences.

Very interesting. Thanks for the information. Given that the TBT prefix doesn’t even appear in the SCSW, I may have to have this pistol lettered to find out more about it. I’ll definitely post pictures once I pick it up from the California 10 day waiting period.

On ambi safeties with the dreaded “loose screw” I find that a drop or two of nail polish applied to the threads on assembly take care of the problem. Just remember to clean threads and renew nail polish each time you dis- and reassemble. Of course the best solution is the Gen 3 safety with spring and plunger!

I will emphatically disagree!

The best solution is a 2nd Gen single sided safety.

Looks fantastic.

Purple Loctite works well too. I had the loose screw issue with my 659, but after a few drops of Loctite it no longer comes loose.

You’ll never be tacticool with that attitude!
Since my Dad was left handed, whatever ambi parts I could find follow me home. Dad’s been gone for several years, but old habits…
Froggie

Got the 639 home today and gave it a thorough cleaning. Compared to my 659 there are some noticeable finish differences:

- The 639 is polished to a much brighter shine, while the 659 has more of a brushed look to it

- The matte stainless sections of the top of the slide are more textured on the 659

Not sure if those are general differences between the two models or have anything to do with different finishing processes being used by the factory when each of my pistols was made.

Regardless, I'm very happy with this gun. I still need to find out more about the TBT serial prefix as it appears to be one of the last Gen 2s made.

Attached Images

639.jpg (152.7 KB, 20 views)

I also noticed that the rear sight on my 639 has been drifted to the left. Did any of these pistols ever come out of the factory with the rear sight off center? I know it’s more likely that the previous owner had it drifted, but was curious if it could possibly be factory adjustment.

Based on what I have seen, S&W was busy changing the level of finishing on their pistols about midway through the production of the second and again midway through the third generation pistols. When the 645 came out and S&W switched to the hooked style trigger guard, the flats of stainless slides received a smoother polishing. This continued into the third gen pistols until the hooked trigger guard returned to a round configuration. At that point, slides were being given a uniform bead blasted finish.

My 645's have smooth, reasonably well polished slide flats, my early production 6906 has a similar finish on the slide, my later production 6946 is all bead blasted. No indication of these being anything other than factory finishes.

The rear sight drifted off center was probably done by a previous owner, but it is possible that whoever was installing the sight at the factory was in a hurry and did not get it centered. Test fire before attempting to center the sight, if it was moved by a previous owner, they may have done it for a reason.

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VCDL, GOA, NRA

I spoke to the person I bought it from. He says it shoots to point of aim with the rear sight where it is. I’m going to take it to the range tomorrow after work and see how it does for me.