In order for your web bag to be Communications related (Mine Detectors also) there is usually (but not always) a ZA part number stenciled onto the bag. In this case there must be another piece missing as the bag should have two small buckles sewn to the bottom in order to receive the shoulder straps, but there are none which would make wearing this bag in lieu of the Haversack very difficult. I have attached images of a 1937 Pattern Haversack to show the strap arrangement.
