TrigpointingUK

Thanks agentmancuso,
I'm still baffled, but convinced there's a trigpoint connection somewhere.
SBs

Thanks for your help. The geocache has been set by a Trigpointer, a member of TrigpointingUK, Dave Johnson. There's a pic of the OS TP symbol, which is why I think it could be a Trigpoint puzzle.

The geocache is https://www.geocaching.com/geocache/GC74XB1?guid=85acef23-0239-420f-809e-8aa151f8a61f ...

Dear All,
Is there any trigpoint significance in the following letters:
B C D F H J K M N
They have appeared in a geocaching puzzle concerning (I think!) trigpointing
Kind regards