This cache is part of the Cwm Rheidol Expedition series. Whilst
each cache in the series can be treated as a traditional cache,
they also have two letters enscribed in the lid which can be strung
together to form a web address. In turn, this will give you the
location of this cache.
To get the location, visit http://blog.pacifist.co.uk and click
on 'Bonus Geocache' under 'Pages'. The password is eight letters
long (all capitals), and the order of the letters is specified on
each of the cache pages.
Congrats to avapoet for FTF