The discussion on this thread might help regarding the splash copper rooster.
https://www.backyardchickens.com/t/652622/marans-rooster-blue-copper-splash
Blue, Black, Splash Marans (aka... BBS), solid birds that do not carry copper genetics and Black Copper, Blue Copper and Splash Copper are 2 different color varieties of Marans, so when speaking of the Blue Copper variety and Splash Copper varieties...then a person would see copper in the Splash that come from copper genetics.
Solid BBS Marans should not carry copper and should not show copper as they are suppose to be based on silver. True solid BBS birds are pretty rare and IMHO, alot of "BBS" Marans are Marans that have copper genetics in their background somewhere. It's very easy to assume a melanised BCM or melanised Blue Copper as a solid bird as some melanised birds can appear completely black, blue and splash.
SOMEBODY CORRECT ME PLEASE IF I AM MISTAKEN IN WHAT I SAY IN THE PARAGRAPH BELOW....I don't want to give the wrong info.
When the 2 varieties are crossed it can create offspring that carry one copy of each gene, 1 gold/red (not sure if gold and red are considered the same here) and 1 silver. The silver can produce birds that can show color in the hackle, wing bow and saddles, lighter than should be, ie... cream/yellow or gold. If the Coppers also carry Mahogany, Mahogany will show as red in the shoulders of the males, but I am uncertain of the effects of Mahogany on silver based birds.
Hope others come by to post their opinion and I hope this helps and I didn't confuse anyone or anything or give the wrong info.
Thanks for the info. This does explain it pretty well. The chicks I hatched from this person's eggs are not really showing splash characteristics but they are only about a month old. I'll have to wait and see how they feather out.