A rare set of Henselite Indoor model bowls in a size 5H, stamped BIB 1998.
This model is no longer produced. It was made, as the name implies, to provide a tight line on fast indoor surfaces, and was eventually replaced by the Henselite Tiger II
About the International Bowling Board date stamp
In 1986 after much discussion a new Reference Bowl was issued to all manufacturers and testers and the IBB stamp became the accept date stamp through out the bowls World replacing local National stamps such as the BIBC (British Isles Bowling Council) stamped used on bowls in the UK.
For much more information about the evolution of testing and stamping, see http://www.thesportofbowls.co.uk/bowls-date-stamp/