Plating with an Alloy of Silver and Gold

A. Yes it can be done, but it is complicated. You can use cyanide based solutions or even cyanide-free. Ferrocyanide solutions are simplest and probably oldest cyanide free solutions (1841-Elsners ferrocyanide based gold plating solution!) Probably thiosulphate based or pyrophosphate based solutions can be used too (try uspto.gov webpage -USA patents database, there you can find at least 1 patent devoted to thiosulphate based gold, copper and silver baths). Probably you know that cyanide based solutions are very dangerous stuff, so for DIY work I must recommend you only use cyanide-free solutions. You can use gold or silver bath + add some water soluble copper salt, or copper bath + add gold or silver water soluble salts. Complicated, and need lots of experiment, but as I said before it can be done. Hope it helps and good luck!