One more thing I learned today? Due to high inflation during the Civil War, people began hoarding their coins, leading to a huge shortage. Businesses began issuing tokens made of copper instead, which were used by customers in place of real money.
They should bring those back, be good for a little boost on a long day (couldn't be any worse for you than chugging a couple redbulls...)
They are the initials of the letter writer and the initials of the typist.