R.H. wrote:

In my post concerning the pen, pencil and knife, I forgot to link back to
the answer page where I've posted a new photo of set:

http://pzphotosan111-r.blogspot.com/

I also think that the knife was used for erasing. I did that many times
when drawing plans on transparent paper with black ink. You get errors
only off with razor-blades or the like.
Because the surface gets rough by scratching, you would get raggy lines
if writing over that spot again. Either smoothen it with the flat of
your finger nail, or with the handle of the knife (see below). Depending
on the radius of the glass(?) balls in the end of the handles on your
photo, they might be used for that purpose.
My dad, who was an architect, had a special knife for that purpose,
albeit it looked different.

Nick
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