Rheingold is not a currency, but a medium of exchange used in Dusseldorf Germany since 2006. It is a voucher.
Previous in the trade page, Rheingold is described as "a currency pegged to Bitcoin". However, there is no mention of such peg in www.rheingoldregio.de .
It seems it is offered by an independent website schweinehaus.de for a 1:1 exchange rate on 8 January 2011.