richard wrote:

A recent electrical inspection /test of an industrial premises owned
by my parents says:-

Crabtree MCbs BS3871 cat M3. Have no type number, recommend replacing

does not comply with BS7671...

Pah!

My question is.. are they obsolete???

Obsolescent, perhaps - their catalogue says this:

"The tried and trusted Magnetic/Hydraulic mechanism
of the C50 remains as before, albeit in a slightly
reduced range. The Enclosure system for the C50
MCBs however, is undergoing some dramatic change.
The old enclosure system with separate Enclosure/
Interior and ‘dished front plates is being phased out.
Current stocks, once exhausted, will not be replaced.
The New C50 Enclosure System will utilise a modern
style enclosure with doors fitted as standard, but will
only be available in assembled format with 100A
or 200A Incoming Isolators prefitted."

Download the industrial circuit protection catalogue section from he
http://www.electrium.co.uk/download.asp#pos_crabtree

--
Andy