Abstract: It is desirable to ascertain the amount of grain passing over the sieves and the like of a combine harvester so that adjustments can be made to reduce this loss to a minimum. Acoustic, electronic and other involved devices are available but these are relatively expensive, and, if faults occur, difficult to replace and/or repair, particularly in the field. The present device is basically mechanical and comprises a hinged frame under the harvesting machine just forwardly of the straw and chaff discharge with a cover plate hinged to it and a drop box detachably held in the frame. When in the closed position it is held by a latch which, when actuated, releases the frame and drops the rear end by gravity onto the ground and holds the cover up so that the drop box slides free of the frame onto the ground. When the straw and chaff discharge passes over the drop box, it collects a sample of grain discharged with the straw and chaff.