Wow, lots of great information for the masses being posted here
For the record, my gun had intact seals, and did not in any way appear to be futzed around with. While I am disappointed in how TA chose to handle the failure, as a business I respect their decision. Up to this point, I have never had any trouble with TA, even when I had to return a couple of items (both without incident). I file this whole thing under "dumb on my part" and have moved on... (granted, SOME form of "gesture in kind" from TA would have been appreciated).
Now that THAT's out of the way... the gears have no stamps/markings on them, the gearbox seals were intact, and overall the gearbox was nicely (but not perfectly) assembled/shimmed. I don't think anything was built or put together poorly except for the piston, which I think suffered from a casting defect or similar flaw.
The gun is now back together, having had a Lonex piston, hop up, and shim set installed; and is now in the final stages of tuning
Anyone have some experience with a Lonex hop up in an Ares G36? This thing is a bit of a b**ch to install/tune...
As always, thanks for the feedback guys and gals.