I've written about this before on this forum.
A long time ago, I got the idea of abrading off the gold plating. We first tried tumbling the parts in a small rock tumbler, using various media. We tried it both wet and dry, without much luck. I still think it would work if the conditions were right - maybe with a vibratory finisher.
I then found a company that made sand blasting equipment used for small items, like nuts and bolts. This consisted of a rotating, rubber coated, mesh basket mounted in a cabinet. The basket was tire shaped and was mounted vertically. In the front was an opening, into which the downward pointing blasting nozzle was mounted. The parts were placed in the basket. As it turned, all portions of the parts were exposed to the blasting sand.
I took a variety of plated materials to the manufacturer, who agreed to let us play with various blasting media. To make a long story short, the best was tiny steel shot peening. The peening action flattened and stretched the plating sideways. This broke the adhesion and the plating fell off. Everything we tried worked completely, including rhodium plated jewelry. To collect the plating, the shot could be continually (or, batchwise) separated with a magnetic separator and the shot reused.
