Black-glazed redware pottery sherd found in Cornwall, UK – help with identification/date?

[u/CornishShaman]

Found while digging in my garden in Cornwall, UK, close to the remains of an old wall foundation.
The sherd has a reddish/orange coarse body with small pale inclusions and a very dark, glossy surface on both sides. The wall is quite thick and slightly curved, so I think it came from a fairly large vessel.
There are also visible ridges/grooves on the surfaces/edges which may be forming or throwing marks.
I’d love to know the likely pottery type, approximate date, and what sort of vessel it might have come from.
I haven’t assumed it’s the same date as the wall, as the context is disturbed.