From the research I have done, gold washed medallions did not appear until after the 1893 Chicago Exhibition. Many of the highly engraved S&Ws shown had pearl stocks, but all were plain, without medallions.
Gold washed medallions were started in the late 1890s and continued into the early 1900s. There are several threads on the subject and below is one of them.
http://smith-wessonforum.com/s-w-ha...233-s-w-medallions.html?680233=#post141496908