Curly,
Since your Model 70 is a leftie, that might make it a bit tougher to answer your questions. But, based on your serial number, 1997 is no doubt pretty close for the year of manufacture, and apparently 1997 was the first year of manufacture for left-hand Classic actions as well. In right-hand actions, the stop screw on the bolt shroud disappeared some time after 1996, but apparently before 1999. The bolt shroud without the stop screw was probably phased in over a period of time anyway, and may well depend on the model just when they were phased in. The flanged bolt shroud started to appear in 2003 on right-hand models anyway, but I have seen a stainless Classic that I believe to be of 2002 production with the flanged bolt shroud. On the other hand, I have seen left-hand Model 70's that were very late production, probably 2005, that didn't have the flanged bolt shroud.
In rack grade Model 70's, the first model to have the one-piece bottom metal, that I am aware of, was the Ultimate Shadow, introduced in 2003. Some models never did get the one-piece bottom metal. The Classic Stainless model had two-piece bottom metal all the way to the the bitter end, I suppose because the inletting is different for the one-piece bottom metal, and USRAC continued to use the same old stocks, which were inletted for the two-piece bottom metal.