Business card

Business cards were small pieces of cardboard which tended to have their owner's name written on them.

The Eleventh Doctor, while posing as Sherlock Holmes to investigate the activities of Walter Simeon's Great Intelligence Institute, found a pile of business cards in his office. He deduced that they were Simeon's because, as he pointed out, "it [said] so on the front". Simeon was unimpressed, but the Doctor waved the card in front of him for a moment longer before discarding it and moving on to abusing the newborn Great Intelligence in its globe. (TV: The Snowmen)

Behind the scenes
In NOTVALID: The Doctor of War, a story written by Steven Moffat which is not considered a valid source on this Wiki due to its parodical nature, the War Doctor had business cards printed with his new alias of "Mister Moody" shortly before discarding said alias for not being awe-inspiring enough.