matt black finish on copper-plated steel

[typewritermuseum]

I'm restoring an 1890s typewriter. Originally the type bars on this machine had a matted black finish over copper plating. Most of this has been polished off by someone who preferred the bright shine of bare steel.
I want to put the black finish back on, but have no idea how it was done.
I can manage the copper plating, but wonder how the black was done.
If you can help, please let me know.

[mcaswell]

Probably by applying an antiquing agent to the copper. See http://www.caswellplating.com/aids/metal.htm

[typewritermuseum]

thanks

That looks like it! thanks