I carry a 642 Airweight in a kydex "Aholster" (Allen Holster Co) in my front pocket, and love it as a backup. I've noticed that the finish on the side of the frame towards my body is coming off. I initially thought it was a buildup of sweat/dirt and tried to remove it with Hoppes 9 and a nylon brush, but soon realized that it is a coating on the metal - something like lacquer. Anyone know what it is and how to restore the finish...? And how to prevent a recurrance in the future?

All I have heard is that its some form of clear coat. I'm sure it can be fixed if you find out what it is.
The gun being alloy and stainless, it shouldn't be a problem if you don't, though.
It will more than likely reappear anyways. Call it "character wear"

I believe, based off your description and my past experience, it is probably the clear coat that Smith and Wesson puts on the 642 to protect the finish.

Some folks have an issue with it coming off and some folks don't.

Mine came off several thousand rounds ago because I carry the 642 a bunch. It hasn't affected the gun one bit. Just a matter of appearance.

Some people have polished off the finish with good results.

I've heard mixed answers about whether or not S&W will refinish it under warranty.

The best advice I've heard regarding protecting the existing finish is to wax it. I will hopefully get around to trying that with my new 642. My old 642 had really bad finish wear, but it didn't affect its function so I just left it as is.

What kinda wax?
I know to use CLP or M-Pro 7 to clean the Scandium or especially the Aluminum Airlite Frame guns as well as the Ti Cylinders. You could probably call S&W and get a different answer everytime though. That "clear coat" doesn't last, though, whatever you do. I've pulled the grips off Safe Queen Guns and they have those crazed lines and small patches that seem to start under the grips and then work out from there. Wiping the gun down with Eezox CLP will help delay this.
Bottom line, if you actually use or carry one of these Airlite aluminum frame guns it will have some finish issues, for sure, after a while-the SC Serial # Scadium Frame Guns, not so much. If I knew what I knew now, I would only get Scandium Guns for actual carry. This has been my experience.

Rennaissance Wax is what's usually recommended, but I've also read that Johnson's Paste Wax works well.

I have a container of Blue Wonder Armadillo Wax, but it's been sitting in my accessories box for a few years so I have no idea if it's still good.

If you do a forum search you should be able to find plenty of threads on using wax to protect a gun's finish.

Thanks! Yeah, the Search Feature usually works pretty good.

I like that! I'm sure not going to waste time trying to fix the finish on my 642 - it's a pocket gun (and not even a very expensive one), I expect things to happen to a metal object carried in there 8 to 14 hours a day.

Thank you, gentlemen, that's sorta what I expected but was just wondering if my experience was unique caused by something weird I had done. In any event, although it isn't exactly pretty, it still gets the job done!