my first was early 08, and aside from a serious individual QC problem, it worked extremely well (extractor did not actually fit into the slot, it was too wide. It was forced in by an assembler at the factory, but did not move correctly. 20 minutes to remove, shave with two sharpening stones, and reinstall and its worked for thousands of rounds), my second, around late 2008, had the systemic bad chamber issue that the express became famous for. Every 3rd round jammed, sometimes every round. Before the issue was well known, and the fix well understood, it was mostly limited to chemicals to clean the plastic fouling, and extractor work. Anyway, based on my, and a few known others the problem showed up sometime mid 08, around the time the Obama panic started.
Remington had its AR market thing going, so it makes sense.
EDIT: I never had the rust issue, and I shoot in the rain. Shot a lot in the snow. I oil it when it gets wet, or cold (condensation is the common cause of rust in W. WA). my finish is a quality Parkerize in black. Its held up with a few scratches, just like any other Park stuff. After chamber honing, they all work fine, including those others I worked on. I have never seen one with a poor finish or rusting issue in the hands of a "gun person", however, the 870 has a major following among the shoot it and ignore it crowd, and ALL good shotguns with their high-carbon steel barrels are prone to rust more than other types.