Just looked in my old yellow reg book , Type 1 miniture circuit breakers to BS 3871 .Its max Zs is 2 for a 30a for 0.4sec dis time reg 413-02-11 and 5sec dis time for reg 313-02-12/14
It won't be type B it will be type 2 - letters are used with 60898's. A type 2 breaker is exactly the same as a B type, so a 30A will be 1.60 (100% value).
thanks for the replys i thought it was strange been a type B it was a retro fit wylex i had to look twice but it was defiantly stamped type b 30a on the case
I was about to ask if it was one of those nasty Wylex things. It's definitely a type 2, and besides those values are the safer of the two.