The research conducted by Ivan Metchev on the so called “Sofia” issues is undoubtedly one of the most extensive and in depth studies on the subject in recent years. It brings together a large volume of visual comparisons, observations on clichés, statistical d...

A few decades ago, philatelists did not face many of the problems that are now completely common. In the past, the main interest was in used (cancelled) stamps, and the requirements for mint stamps were minimal. The issue of missing or damaged gum was almost n...