Two raiders, one armed with a knife, threatened staff at an office licence in Lichfield before stealing cash and a worker's purse.
The robbery happened at Threshers in Wheel Lane at about 2200 BST on Monday.
Detectives have appealed for witnesses after the men got away with money from the till. No one was injured.
Police said they escaped in a small red car with a registration number thought to be S589 OVP.
Both men are in their early 20s and speak with Midlands' accents.
One is 5 ft 7 ins to 5 ft 8 ins, white, slim, with rotting teeth and a dirty appearance. He was wearing blue jeans, a charcoal grey hooded top and a blue Timberland woollen hat and trainers.
The other is 6 ft tall, black and well built. He was wearing black jeans, a black bomber jacket and a black woollen hat.