Well, as you're asking, the one pictured above came in a job lot of S/A Parts. So I dug out the one from my basket case Longstroke A7 Motor.
This one is slightly different,with a more concave end to the outer edge, rather than the tapered shape. Otherwise they appear identical, pictured side by side (Longstroke on the left) to show no difference regarding the breather holes and drive peg location. Bear in mind these parts may be the correct ones or entirely spurious.
Surprisingly neither open the breather vent fully in the inner case. In other words the holes don't match completely and coincide perfectly as you would expect.
Never noticed this before, but got me thinking. Is this how they all are, and why we get problems?
Baffle insert is deeper on the S/A breather, 11mm, compared to 9mm for the Longstroke. All other dimensions are the same.
The Longstroke uses timing gears with different timing marks, allowing the use of a common breather on Longstoke and early Shortstroke motors.
Swarfy.