'P' is the key

[Loose_Spell_9313]

If you can point to a point of reference where this is clarified

This one is easy. The Library of Congress entry makes the following reference:

Further description of map appeared in article: Bagrow, Leo, 1948. The maps from the home archives of the descendants of a friend of Marco Polo. Imago Mundi, vol. V.

The article is available on JSTOR with a free account. Quoting from page 6:

The map is now in the Library of Congress. The dimensions of this map: full size of parchment - 40 X 28 cm; size of map (maximum extent measured) 19 X 26 cm.

I think we run into the same issue though, because yes, it says size of parchment size of map- but again, how does one determine what parts are a map without knowing the contents beyond the box? I see the logic for "map, rectangle" don't get me wrong, but I just dont know how one would apply a uniform measurement to that in a way that is non-speculative. 

Even the JSTOR literature uses a variety of the terms that create some ambiguity: parchment, vellum, and map. Vellum and parchment are different materials. 

Anyway, I think my argument is still there's lexical ambiguity.