What indicates1892 Winchester barrel replacement?

Answer 1

The original factory barrel will have the name Winchester and the chambering of the gun stamped into it.
The color is another tell, the color on the chamber should match the barrel exactly.
Look at the joint between the barrel and the chamber, can you see any bare metal at the end of the barrel?
A replacement will have to have had the threaded end of the barrel milled after it was blued to get it to fit right.