the first new currency post-collapse will probably be made out of gold. it's value in history wasn't because of the fact that its shiny, its because its physical properties make it the best candidate for a lasting currency.
gold has been the main standard of currency for all of human history up until 1973. not that much has changed in 44 years, its just a matter of time.
The hardcore prepper books I read disagree and go with silver. Gold will likely still be too valuable to conveniently barter with once shit calms down.