By special request here are pictures of my Baccarat grape vase. A very similar one is depicted in Cappa (p.178) in gold ruby.
Apparently, Baccarat bought the patent from an outside inventor and refined the procedure. This vase is from 1878 and counts as a precursor to the proper Cameo technique.
Cappa describes it as clear crystal cased with a colour layer, then press moulded. The design achieved by acid etching, leaving the design behind. Background satinated, relief polished.