SA Type 2 with no drawing #?

[1563621]

It is trackless. https://imgur.com/a/gFfYZBN

[RCS]

I don't know what SA Type 2 means, but my opinion is that the first three apertures are aftermarket

[1563621]

SA

Aperature

B8868-1

Type 2

November/1939 to February/1940

20000 - 28000

No tracks on the bottom of either side of the teeth and drawing number omitted.

WRA

Aperature

B8868-1

Type 1

December/1940 to January/1945

100101 - 2540999

Parkerized stamped steel. May have punch mark on bottom surface. 60 degree crosshatch pattern on face. No tracks on either side of gear.

[Orlando]

middle two are aftermarket for sure

[RCS]

Got this aperture from Mac years ago, short life period in service.

[RCS]

without drawing number too

[1563621]

middle two are aftermarket for sure

Agree middle 2. casting marks.

[1563621]

So the first one is correct?

[RCS]

mine is original and has 17 teeth yours has 16 teeth. Need to compare the first aperture with another with the drawing to be certain.