Went back again to the Rainhill Hospital land for another walk around. Plenty of common bricks around but then found this special plinth brick. Since there was no buildings around to explain its presence on the land. This is likely to be from the hospital after is demolition and was not removed.
Not seen an Accrington NORI brick like this before and it may have been specially made as an order. It is now part of my collection.
No idea of its date but Rainhill Hospital was built in 1851 and closed in 1992. So the brick possibly came to St Helens in the 1800's when the hospital was first built.
The brickmark is on the underside of the brick and can be seen in the Lancashire Gallery.