This item recently appeared on Kjell Scharning's site as a "new" issue, with a monochrome image of three of the stamps postally used as they appeared in Michel Rundschau 4/2001.

I remember something similar happening in the 1980s with two sets issued by Ivory Coast. These were listed very late by Stanley Gibbons, and images were usually of postally used examples. I'm still missing some of these stamps.

Update identifying species on two of the stamps.

Further update showing all four stamps.