Stopped by the local stamp store on my way home last night and picked this one up along with a few others. I don't have many Revenue Stamps yet, but have been keeping my eye open for some 1862 cancelled stamps. This R48a is courtesy of the Illinois Central Railroad.
It's Maryland Stamp & Coin in Bethesda. They have a huge online presence for stamp supplies. The brick & mortar section is really small though. However, being one of the only stores in the area that I know of, people bring their old collections in to sell. David, the guy that's there when I go in on Thursday evenings, let's me look through the lots that he's bought but hasn't had time to go through. Pretty cool opportunity.