Our Legacy Royal Coster Diamonds, 175 years of craftsmanship The world’s most trusted diamond factory has a rich and compelling history. In our diamond facts section, we discuss some remarkable facts about diamonds in general or about the legacy of Royal Coster Diamonds. Today we discuss the subtitle of our famous logo: Since 1840. Royal Coster was actually founded before that date, but we just can’t proof it. Here’s the reason why.