Ajman is a Persian Gulf sheikdom that is part of the United Arab Emirates. It issued a few stamps independently in the 1960's, but modern stamps are in the name of the UAE. However, many spurious stamps have been created in the name of Ajman. They are all relatively cheap and are not even catalogued by Scott. This stamp seems to be a photograph of Schweitzer playing at an un-named console. If one knew details about the image, one might be able to determine which instrument it is. As it is, the caption "giving a concert" is not enough to know much more about the stamp.