Manual states 90 psi....interesting...I'll have to go down to the shed and see what mine has on it.
Not the easiest thing to get a photo of, but it is stamped '70'.
"Oil Pressure Relief Valve
Release pressure 85-75 p.s.i."
BSA A75 manuals state "Blow-off pressure (oil at 80°C) 70-90 lb./sq.in."