Holding a Mint carries the right to control issuance of
units of a particular currency.
Purses and payments associated with a particular assay can only transfer value to others using the same mint.
The primary use for Purses and Payments is for currency-like and goods-like valuables, but they can also be used to represent other kinds of rights, such as the right to participate in a particular contract.
Purses hold verified
units of certain rights issued by Mints. Purses can transfer part of the balance they hold in a payment, which has a narrower interface.
Payments hold verified units of certain rights issued by Mints. Units from payments can be deposited in purses, but otherwise, the entire unit is available when the payment is transferred. Payments can be converted to Purses.