the storage mechanism can't be coins
The storage mechanism could be coins.
Unfortunately, coins have been out of circulation for many years.
Coins have an intrinsic value (as in gold or silver).
Tokens
represent a value, but have no actual value.
If the world's governments began issuing coins instead of tokens, we could once again carry some value around in our pockets, instead of just 'promissory notes', which are basically IOU's from the government.