Radio tuning unit for military radio by Rockwell Collins. This is a fibreglass double depth drum (two drums mountewd on a single aluminium core, packed with coils and resistors on the inside and contacts on the drum periphery and end sides, used in conjunction with other similar drums to select the correct frequency. Manufacturers part number: Assy: 554-6089-004 NSN 5820-00-057-1896 (updated number to be confirmed) Status: NOS (New Old Stock) Ex USAF stores, in original packaging. Unused so all conacts are unworn.(slight silver tarnishing, that just rubs off) RoHS compliant: n/a