6-Foot Starter Assy 

In Ken Philp's book “Neracar” on page 72 it can be read that Model B had an eccentric pin to adjust the teeth mesh and the accessibility of the locking nut was improved as well.
The nut of 134-Shaft,  Foot Starter Assy is very inaccessible, so it looks like a Model A  shaft has been fitted. On the other hand, it does have an eccentric, which is supposed to be a Model B feature. Three out of four  Model A’s I’ve information about, do. It might well be that there were more in-line changes we're not aware of and that there were (late) Model A bikes with an eccentric shaft.

I made a special socket wrench in order to tighten 1005P Nut, ½” BSF of 134 Shaft, Starter, by cutting off both ends of a box spanner. The height must be such, that the box spanner can be inserted in the front support of 405 Fixed hanger and 134 Shaft, Starter Assy from the bottom up. The extension rod of the box spanner can then be pushed through the holes of both the front and rear support, in order to tighten the nut after 134 Shaft, Starter Assy has been adjusted by rotating it, until the teeth mesh of the Pedal Segment Assy and 621 Pinion, Starter is correct.
In order to have sufficient space for the box spanner, the attachment bolts and nuts of 405 Fixed hanger have to be removed or loosened and pulled up.

 This PPL-set of contains both photographs of 100-Frame Assembly and 600-Engine Assembly. In the Excel sheets it can be seen which Part Numbers show up in what PPL-sets.