Mini Spares Non genuine timing chain gasket fitted to every BMC A series engine with 10 gasket holes until the introduction of the A plus type which had a bulge in its side where the tensioner was fitted which had 11 holes.
Gasket material has moved on since the mini first used this gasket in 1959 and your car has increased in value over its cost, so why not fit the next generation Klingersil gasket. See
GUG705803GM.