This antique watercolor with hex type star at center, done on what looks like the inside of a book's back cover, is just the sort of thing I am forever opening antique books in hopes of finding--but never do! It looks to me this one was deemed special enough to frame long ago, and may have lived in this lovely hand-carved framed since the beginning; perhaps the frame was made just for it, as it fits it exactly. I love the saturated colors and how modern it feels (I'd guess the book was math-related, as someone had their ruler and protractor out!)—perfectly counterpointed by the tiny Stars and Stripes waving at the bottom! 

Framed: 10" x 7 7/8" x 3/4". Sight: 6 15/16" x 4 5/8". Watercolor on board. I might would guess 1860s-70s or so on both watercolor and frame. There is one small rough spot on the drawing along the left edge; overall very good condition and the frame is in excellent condition. One nail securing the horizontal bar across the back is loose due to a split in the wood; a little tape will hold it very tight or another solution could easily be improvised.