Well hopefully the price is right - shame about the boxes and papers - worth fair bit more with them and don't forget you will have no tags or booklets.
The 16800 is nice watch, sapphire crystal and trit dial, older steel used, so the last of the 316L cased Rolex Subs. The 168000 and 16610's etc. moved on to using 904L.
I have no idea how you would tell the difference though.
You would ideally like original dial and hands, good solid case and decent bracelet with not too much stretch.
Fingers crossed and you may well end up with a nice modern vintage subby :)