This was an interesting attempt to market small gold ...nuggets. To quote the flier accompanying the brochure:

The Gold Card comes with the flier quoted above (with more information than shown above) and a nice card stock brochure. The front of the brochure can be seen to the right (shown actual size). Each gold card contains a flattened nugget weighing 6 grains.

The back of the gold card gives a brief description of the process (shown above at a reduced size).

These are available for $25 each, postpaid. This is just another example of how miners tried to enhance the value of their gold and avoid sending it to the refiners.