This happened today at 7 AM. He was 7 times 10x10 World Champion, many times USSR Champion, many times USA 10x10 Champion, author of more than 40 books.
Obviously a real epoch go away with him. This is a great lost for checkers fraturnity. His role in checkers (10x10) was at the same level or higher compare with role of Mikhail Botvinnik in chess. Iser Kuperman was patriarch in checkers.
My deep sympathy to everyone who knows him, the whole checkers fraternity, FMJD and family members.