1861-67 Benjamin Franklin One Cent Stamp Addressed Envelop

1861-67 Benjamin Franklin One Cent Stamp Addressed Envelop No letter in the envelop. Stamp looks to have been stamped with the letter I or U in a blue color. I am not a stamp guy so I have no idea how to date these things, just thought this was  a neat item tucked away in the pages of a book from the 1860's and was used as a page mark. The envelop is sealed so the gum resealed itself at some point. The gum from the glue has turned a ruddy yellow color. Please do check out my other items as I am happy to consolidate shipping!This item condition is overall fair condition. Do note my return policy, this item is sold as is no return - so if you have any questions, please don't hesitate to ask.This item will be shipped via USPS First Class Mail. IVL - B1