Police said the man went in to the Friend Jewellers in Cape Hill, Smethwick, wearing a burqa and pushing an empty children's buggy.
Police said the Asian man was joined in the store by four other Asian men who were all equipped with hammers.
They sprayed four staff members with an unknown substance and smashed display cabinets before fleeing in two cars.
The burqa is a traditional form of Islamic dress for women consisting of a full body covering that also obscures the face.
Staff in the shop were not seriously hurt.
The owner of the shop is now offering an undisclosed reward for any information which leads to a conviction.
Source: BBC (English)
See also: Sarajevo: Robbing bank with Burqa