Dear Wes,
in my opinion, the factory build Windshield frame don´t have the canvas top retainer channel.

The Field modificaded Frames are simple cut out standart frames, that have the channels still on.

The two welded on nuts for the passenger wiper motor are on both, exept the hole for the wiper itself on the "factory build" one.
Or is that a myth?
The M38A1C was not designed to have a canvas top on.
And sorry, the data plates where gone before I get the A1C´s.
One was buils up as a static display for an exhibition in Berlin

the other (same as on top) was converted to a normal A1 "fun driver", before it was sold. All the specific parts are going with it.
But I still have two "normal 1963? build A1´s in the Serialnumber range of 945xx and 948xx with the Kaiser prefix 7105
Sincerely
Frank
EDIT:
You can´t fix the rear seat hooks not on a A1C.
There is nothing to put them on, otherwise on a A1
EDIT 2
Thanks Wes, for that detailed Information about the MWO and part numbers