Hi Craig
I have 2 frames here residing in my living room
Frame 1: Oct 39 - integrated saddle bolt loop - grease nipple at rear
Frame 2: Oct 41 - separate saddle bolt bracket - grease nipple at rear
I can check others here later if you need
I have a feb 1940 & a 44 to hand br
Jo’b
Unfortunately we don't have the circular to check, but it could be that its to do with retro fitting a grease nipple to early machines which didn't have them? This may be evidence that these circulars didn't reach every machine?