According to a Panapress article dated 4 April 2008, with inflation running wild at 165,000%, the Reserve Bank of Zimbabwe introduced 25- and 50-million dollar bearer cheques on April 3.
50,000,000 dollars, 2nd April 2008. Expires 30th June 2008. Issued April 3, 2008. Purple. RBZ logo, signature (Dr. G. Gono, Governor), solid security thread, and Zimbabwe bird as watermark with RBZ as electrotype. Three elephants on back.
Courtesy of Nick Brice and Hartmut Fraunhoffer.