I peruse eBay quite a bit for things relating to Frederick. I've gotten lucky to once stumble upon some life insurance payouts from one of my great-great-grandparents to one of his daughters. I also occasionally bought something in the hopes that I might get lucky again. Below are two recent purchases.
Here is one such document, it's a loan paper from 1853. I bought 20 or so of such documents, most of them are from the Frederick county area, though I did get one that was from Frederick county Virginia. None of them deal with direct family members so I will most likely donate them to the Frederick County Historical Society at some point in the future.
Also note men are still named "of", as in this case, John Flook of H. The dates are from around 1905 so these were probably some of the last people named as such. Again, after copying the needed pages, this will most likely going to be donated to the historical society.