It's rare to find post cards this old and not used.  During my picks, I came across a box of about 50 cards.  All about 100 years old.  Some are used and post marked, some are greeting cards and some are post cards that were never used.  I separated each category and posting on eBay at fair price.  julius bien, P. Sander , w. j. Thompson and Co, Henderson Lith, Cinn Oh,  S. Langsdorf and Co.,  Lot of 8 antique/ vintage post cards that were never used and blank.    One-cent postcards were used in the United States from 1898 to 1901

Antique and or vintage Christmas post cards blank lot .  price tag from an antique store still on the original sleeves these cards came in.

Theses are not personalized or stamped or post marked but some cards do show the amount required to mail.  one cent national,  2 cents foreign mail