I assume you are asking about the barter viability of silver in a scenario where cash and credit cards have, somehow, lost their value.

Additionally, I'm not sure what the conditions are: is it about preserving your overall wealth post-whatever, or bartering with others while on the move?

In any case, I heard salt can be a good investment: it has enormous value when scarce and that value can be easily verified by taste. The downside is bulk, but at least you're not hauling dead weight...