Complex sentence: From 1963 on, commemorative and special issues started to appear more frequently; in the 1990s, typical policy was to issue 5-6 sets per year, each consisting of 4-5 designs.
Split into simpler sentences: From 1963 on, commemorative and special issues started to appear more frequently. In the 1990s the typical policy was to issue 5-6 sets per year, each consisting of 4-5 designs.