Comoros Fauna And Flora Sheet

Hello there.

I have this sheet od stamps from Comoros, but cannot find it in any stamp catalogue. It looks genuine, well printed, similar to other sheets from Comoros (design, dimensions, quality), however this item cannot be found either in catalogues or lists of bogus issues.

I could find singular stamps from that sheet on various auctions. The sellers (always philately shops) claimed that the stamps were "printed by countries authorized press", whatever it means.

Can you help me with this? Cannot believe it could be a bogus, as it had been been so well printed. It must have been issued before 2000 (country name and currency sign suggest so).

Issued 1999, but that's about all I know.

The agents who print this kind of wallpaper use the same quality of production (or higher) for wallpaper as they do for regular stamps. There is a philatelic agent located in Brooklyn NY who is notorious for this approach.