I would add toiletries to the list of barter items. esp. Toilet Paper, Wipes, etc.

On Gold & Silver front 'bullion coins', i.e. those whose value is effectively tied to the value of the material, as distinct from rare old coins made from precious metals, that have a greater value than their material worth are what you should be looking for. Examples of bullion coins include the Kruggerand, Canadian Maple and Gold Eagle.

Take a look at this site from loads of background info, it is in the UK, but they will ship to the US:
http://www.taxfreegold.co.uk/coinsorbars.html

The ETS audience might especially like this coin design:
http://www.taxfreegold.co.uk/2007fiftypencegoldproofscouting.html

BTW Gold is setting record prices at the moment, so it is perhaps not the best time to start building a hoard!