I just upgraded my 1984-vintage panel and added a GTN 750, a GTX 23 remote transponder, and a GDL 88 ADS-B transceiver. I removed several pieces of equipment in the process including a Foster LNS 616 Long Range NAV System. This was state-of-the-art before GPS. It could calculate a lat/long of a departure point and a destination, and "draw" a great circle course line between the two points. It took inputs from LORAN-C and VORTAC stations to compute a highly accurate present position, and presented steering commands to the pilot on the HSI/CDI. Way cool! Is this a collector's item worth thousands, or is it trash? Thanks.