rpress_payment_currency

This filter is applied to use the payment currency, it is including two parameters.
$payment_id-> its containing payment id.
$currency -> is containing currency name.

An example of how you can append additional information:

function get_payment_currency( $payment_id,$currency ) {
// its return currency name.
return $currency;
}
add_filter( 'rpress_payment_currency', ''get_payment_currency);