This Mongolia souvenir sheet issued Jan 5 1993 has a flowers background, gold coloring with the Scout emblem at upper right.  Part of the gold inscription is missing in error.

It would appear the gold foil stamping machine ran out of foil or something foreign got in between.  I found one error sheet in a pile of normal ones.  Both the Nature Conservation inscription and the Scout emblem are affected.  These markings are both above the gold center stamp in the souvenir sheet.

On the error sheet, only NATURE CONS has the gold foil, the rest of the inscription as well as the entire Scout emblem are "blind".  You can see the impression the stamper made when the sheet is held at an angle to the light but no gold foil.