This item consists of a 4 x 7 brass enclosure per MIL-E-24142/4 with a series of indicator lights mounted to the cover that indicate the status of the retractable sheave on the deck of an aircraft carrier. An adjustable bracket and stanchion are provided to secure the item in the proper position for viewing. In accordance with NAVAIR Drawing 617590, Part Number 617590-12. NSN is unknown, if assigned.