If it will be permitted on the SGR board. How does one sell physical gold? I have never done it. Why would they beleive you it is gold?

Ever heard of an acid test? Give it a scratch (in case they've plated it), drop some strong acid (nitric, hydrochloric, sulphuric) on it. If it fizzes, it ain't gold.

The term has since come to refer to any strong test to verify something or some result.