I will be watching this one with a certain hunger. I know how hard it is to find an original sight wheel. I once had to settle on a heatnbeat reproduction (don't take "settle on" as a derogatory remark--his repros were excellent!), "just until I could find a real one." After a couple years of searching, I ended up buying a complete 601 upper just to get the rear sight.
1-14 barrels come along now and then.
Carbon steel early-bend gas tubes show up.
Type A stocks and early handguards pop up from time to time.
But a 601 sight wheel or the horizontal-lines mag button (for an early 01)...those parts almost never come along separate from a complete rifle.
If you are building a 601 clone, and if you are one of us who actually needs the real, correct parts, you should be gathering your dollars right now and be ready to submit your best bid on this one.
I am so glad I'm done with collecting 601 parts!