Purpose of B18 Blankets

[buymycards]

At first I didn't think it made sense that they were pen wipers, but then I looked up a definition of pen wiper:

Definitions
from The Century Dictionary.

noun A piece of rag, chamois leather, or other material used for wiping or cleaning pens after use. Pen-wipers are often made up into ornaments more or less elaborate.

from the GNU version of the Collaborative International Dictionary of English.
noun A cloth, or other material, for wiping off or cleaning ink from a pen.

from Wiktionary, Creative Commons Attribution/Share-Alike License.
noun A cloth or other material for wiping off or cleaning ink from a pen.