Don, the 1754 mention of Walter BRASH was not his birth. It was in the rights to Mortcloth in the Abercorn OPR, a really useful record, thus: "Margaret Meikle relict of George Brash Smith yr has aright both by her husband he being son to Walter Brash in Golphole as also by the said Henry Meikle her father a Contr in person".
George BRASH was a smith in Newton, who married Margaret MEIKLE 12 Jun 1694 Abercorn. Most probably he was bpt 7 Jul 1658 in Abercorn, a witness being George Dundas of Duddingstone, and his father being Walter BRASH. His mother would be Christian JOHNSTONE. Although there is no record of the father Walter BRASH's baptism, he seems to fit into a convenient slot left by seven known children baptised 1629-1649 to Walter BRASH, all born in Abercorn, latterly stated to be Newton there - hence my estaimate of 1632.
Knowing where Golphole was might help support or refute this.