That board is later then mid nineteenth century (~1850), did you mean mid twentieth century? (~1950). Looks like asbestos board. the asbestos is bonded to cement so its pretty safe. Paint it all with dilute PVA and ignore.
Frank
it's only 'pretty safe' if you're not touching it.
The fact that it has Poilite stamped on it is a bit of a give away.It does look like Poilite or similar, if so...
The fact that it has Poilite stamped on it is a bit of a give away.It does look like Poilite or similar, if so...
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