If I understand your original log of S8820 correctly, the photo by Ian Mitchell is of a now defunct pillar that once stood at the very summit, where the OS now have listed only a rivet ("HT TO RIVET IN CONCRETE")?

If so, then it surely merits a T:UK entry of it's own? Though maybe it's too close to do this without admin privilegies. I'm still waiting to add Portpatrick Tidal Gauge Bolt to the T:UK database (it's a Passive Station too), but emails to admin seem to disappearing down a black hole at present.

I see there's a block listed on nearby Mullach Mor at NA 09298 00101. Got a spade with you?