Am 14.03.2021 um 12:34 schrieb RJH:
Just noticed one of the TRVs leaking - from the pin. Tried various thumps,
twists and tightenings, but it's still weeping a little. In my spares box I've
got a number of TRVs that I've 'improved' over the years, but they have
different markings and part numbers.

They both have arrows in both directions, so bidirectional I'd guess. But they
have different part numbers (that resist google), are marked 'GB', and
different symbols. One looks like a comb (radiator?), and one looks like an
inverted 'U':

https://www.icloud.com/sharedalbum/#B0z5idkMwmb0Bb

For the 'comb':

https://en.wikipedia.org/wiki/Keymark