So, the "credits" are more worthless than worthless "Federal" Reserve Notes.

'could be' would be more accurate than 'are' and so far the food seems to be holding up. Faith is one of the biggest components of any currency, straight up barter is the only other option. 'Gold backed' requires faith in the value of gold, and that can drop precipitously when food is hard to come by. 'Ammunition backed' would require trust in those who stockpile the ammunition. I think I would put trust in those who warehouse food much more readily.

Some of the more successful local currencies of the past did have assets backing them at their outset, a European coal mine comes to mind as having issued a trusted note. The Mendo system seems to get cash up front and then backs the currency with food as quickly as it can. The trust will have to be in the volunteers keeping everything going unless the Mendo can, in time, make enough profit to back itself (have debt free food in hand before new Mendos are issued), but I couldn't tell if that was at all intended.

From my seat this looks to be an extraordinary effort regardless.

Mahalo Jason