Copper colour confusion

Hiya everyone
I've had a quick scan down the search results and can't seem to find an answer, nevertheless I apologise if this has already been asked.

I've got a steel screwdriver that's been used for both removing screws and breaking stuff apart like a chisel. I've noticed that the top layer of silver-coloured plating has word off to reveal something like copper underneath. Obviously, not-one makes a screwdriver from copper. Plus it's magnetic.
What is this shiny brown colour? It's doesn't really look like rust - it's not bumpy or patchy, but a single uniform smooth shade right the way along. I've also noticed this effect beneath the top layer of stainless. Could it be what's known as tea-staining?

Just out of interest really but may help with grading

Thanks guys

A

If it is chrome plated then under the chrome is a copper plate which makes it possible to plate with chrome. So if seems logical you might find the copper color showing, Mike.

Spot on Miked!

The process is..

Copper, then Nickel (in some applications), then Chrome. The chrome is very very thin compared to the Ni ad Cu coatings..

Genius - that makes sense. I've seen it on decorative items with a silver coating before, so I guess that's the chrome.
How thick is the Cu layer - and would this affect the grade if it's magnetic or will yards tend to just count this as steel?