A drop pan system for collecting discharge samples from combine harvesters or other conveyed machines or implements features a support housing attachable to the machine, a drop pan receivable in a nested position within said housing, and a magnetic hold/release mechanism with electro-permanent magnets responsive to selective energization to switch from a holding state emitting an external magnetic field for holding the drop pan in the nested position, to a release state cancelling said external magnetic field to thereby release the drop pan from the housing. A power supply is positioned on the housing at an area that resides within a footprint of the drop pan's nested position. Differently sized drop pans are included, and the housing features alignment guides for self-aligning the selected pan during magnetically aided placement thereof. Electrical components of the housing are contained in an enclosure that doubles as a support for the electro-permanent magnets.
