Petrol Pump Diaphragm

[B.S.F.]

Which is the earlier type diaphragm for a 2.25 petrol pump, the one with a small slot, or the one with the double cut-out in the stem? Is there a way of telling which one is fitted by looking at the pump? .W.

[67hardtop]

Double cut out.
&
Nope.

Cheers Rod