Carboniferous, Visean, Wardie shales.
Collected from Wardie point, Edinburgh Scotland.
Largely considered to be the pyritised coprolites of fish, Megalichthys was around at this time so that's certainly a possibility but getting it down to a species level would be near impossible.
There has also been a recent suggestion that it could be fish vomit!
The specimen has been polished and measures 69mm x 49mm.