In 1867 the pottery of T Tough & Co in Portobello, Edinburgh, was bought by Alexander Buchan and Thomas Murray. They traded as Murray and Buchan, changing to A W Buchan & Co in 1882 when Murray dropped out of the partnership. They moved to larger premises in Crieff, Perthshire. FROM HERE
That was the simplest description. I would guess yours is more toward the 1880 period but don't quote me.[]