NHER 17242 (Monument record) - Medieval/post medieval stone trough, garden of The Firs

Stone object, almost square (53 x 58 cm), 33 cm high. Hollowed out inside (sides 8-9cm thick) to form trough or tank. Corners rounded. One side has a double groove across it near and parallel to the base, with a chamfer between, converging in the centre to a single groove before dividing again.
Suggests this side was meant to be seen.
Stone is hard and white (but weathered and mossed).
Photograph (S1) in file.
Owner states that this object was purchased from Norwich Castle in 1897 (?) when the prison was closed and many fittings sold off. Her father was told it was used by the prisoners to wash in.
She had recently been told it could be Norman.
Purpose of the object is obscure but it could indeed have been used to hold water beneath a spring or pump.
Probably medieval in date or 16th century.
E. Rose (NAU) 12 May 1981.