For your consideration: a rare Mostek MK3874 piggyback microprocessor chip from early 1980, with a 2716 EPROM, which was the prototyping version of the MK3870 microprocessor that was used in the early RCA CED Videodisc products.

This item was discovered during a cleanout at the RCA Laboratories where the RCA CED Capacitance Electronic Disc system was developed.  The label on the ROM says "9/18/80 E.S. DAXI 1.52 MHz," about a year before the initial release of the CED system.  DAXI stood for "Digital AuXiliary Information" and told the Videodisc player which frame it was currently playing, allowing it to detect groove skipping and correct it.

Don't miss this chance to own both an unusual processor and an artifact of consumer electronics history!