Late to the thread I know, but back in the 1960's my father obtained the slate from a billiard table that had been damaged. The old treadle sewing machines were being abandoned everywhere and he got some from a local lane where they had been fly tipped. Threw the machines away and used the stands fitted with tops made from the slate to make some garden tables. Kept one and sold the others. They are still giving good service.
G.Harman