Kalunga,
Thanks for the info.
Interesting that Gibbs wouldn't fit them, especially for a customer such as Selous!
I suspect that many guns were sent to Beasley for retro-fitting.
I wouldn't want to assume that every steel plated gun was made expressly for Selous, Bell or Pretorius...
I have never seen a copper example but they would be much easier to fabricate. Annealed copper could probably be hammered over the wood and then rolled smooth with a small english wheel.

BTW, is the rifle in the famous picture of Selous with the two Bustards actually a Woodward patent H&H and not a Gibbs Farquharson at all?