The notes below are examples of the initial series. All notes bear country names but have a common design for the reverse. The only other similarity in design is the color (red for 500, blue for 1000, brown for 5000, and green for 10000). The 500 franc notes were all supposed to carry the image of a young girl, but Bokassa insisted that his image be displayed on all notes of the Central African Republic. The first few issues of the 500 and 1000 franc notes are engraved and printed by the Bank of France. From mid-1978 on, they are lithographed and printed by the French firm Oberthur. These notes were introduced over a 12 month period and some carry the early signature combinations 3 (500 francs below) or 4 (1000 francs below). Notes with these signatures are quite scarce and about five times more valuable than issues with subsequent signatures. Block numbers and control numbers are an anti-counterfeiting device from which one can derive the serial number; collectors often use them as a quick guide to mark date or printing changes.