Found on a hill by my 8 y/o, half buried in grass and way off any recognisable path. OS I guess signifies Ordnance Survey, FP – footpath??? What does the 46A mean? what sort of marker is this and what was it used for…?

Found at SD 98436 07635 (ish!)

Likely a sex thing. Probably nasty stuff

Secret nuclear bunker marker stone.

Land owner boundary marker. Loads in Gloucestershire like this as well.

Baby robin. It’s why they are so rarely seen as they are disguised like this.

.

It’s a warning to tell you the amount and quality of frozen sausages buried here.

Keep them coming. Clearly @redthunder is trying to soil the discussion in talking nonsense here.

It’s a fox anchor to give posh people on horses a headstart.

It’s an early version of Tinder.
They were markers left at popular meeting places.

46 A ( 46yrs old – Athletic)
F P (Full Performance)

O S (On Saturdays)

I think I’ve seen that. Is it near 46?

46 A ( 46yrs old – Athletic)
F P (Full Performance)

O S (On Saturdays)

Aaaah Saturday! Jesus the number of Sundays I’ll never get back!

^ all wrong
obviously a bone from a dinosaur replicant

Well done, I was expecting a little red X in a tiny white box

O S (On Saturdays)

I always thought O S meant “Own Spleen”…

A gravestone ?

They recently found the gravestone of the oldest man in the UK, aged 146.

Miles from Belfast.

Did Miles leave any relatives?

It’s a secret entrance to the Lost island.

It’s a secret entrance to the Lost island.

That’s obviously wrong, it’s clearly the lost entrance to Secret Island.

A dinosaur’s vaccine passport

(It wasn’t really a meteor that caused their extinction)

It’s a Canadian 46

Is it a seat reservation? Useless with out the ticket counterpart.

Shermer75, chapeau.
APF

Neolithic bus stop

Its a secret e-bike fast charger point.
46Amps
Full Power
Outside Socket

ZX Spectrum.

Is it MOD land?

Plenty of excellent suggestions up there, highly entertaining.
A slightly more serious answer, possibly, is that you’ve come across this OS buried block although if your grid ref is anything like accurate, it’s wandered a good couple of hundred metres from where it ought to have been, which is a site just uphill from the footpath and near the top of the hill. No better ideas than that to be honest.

Thank all for these highly entertaining answers!

Cheers @thelawman. The hill it’s on actually has two summit (lower and greater Knott Hill.) the obvious peak on the map you point out is ‘Greater’, but ‘Lower’ is nearer to the location, probably 20-30m away.

Interesting that the only visitor to it ‘couldn’t find it’ it would have been buried under heather until 2019 when there was a huge moorland fire and cleared everything out.