Thomas Rawlins was the master of Mint Master during the Civil War. He created the only City view on a coin, the coin was a viw of Oxford in 1644 showing the walls and details of the City. Later when the City fell to Parliment the walls were destroyed. Rawlins very carefully engrave his monogram into the wall of Oxford creating a monogram. We can wonder today 350+ years later that if he new this secret wouuld make his coin one of the most sought after pieces of British coinage.
Above is the TR monogram filled in so it is easy to see, the wall portion is just below
the forward hoof of the horse, the engraving is detailed and can be seen below in
the photograph below.