My personal opinion would be be that the metal seems to be unfinished, and that the wood, most notably the butt stock, has been refinished. I can't see the forearm good enough to make a statement on that although it does look darker than the butt stock. From my experience, the wood should not be shiny or glossy at all.
As for your serial number of 688498, both ProofHouse.com and my own personal Winchester Dates of Manufacture book have the starting serial number of 668058 beginning in 1920 and the starting serial number of 689790 beginning in 1921, so according to those references your 1897 was built in 1920.