Chris

I tend to agree with your interpretation of the unit mark except that the sub unit of a cavalry unit was the Eskadron (squadron).

You're right - you don't tend to see a lot of unit marked 84-98na - presumably due to the decline in their use as the war progressed.

Bright finished bayonets from WW1 were blued overall when used during the post war period.

The blueing on this one does seem slightly strange. Wouldn't like to speculate with seeing photos.

Hope this helps a little.

Regards

Richard