6.5V 2.75A 1460-X microscope lamp
This lamp is used primarily in microscope illuminators by Bausch & Lomb and others.  It is an incandescent lamp with a double contact base with a round flange that has three holes for mounting the lamp.  The "X" in the part number indicates the contacts are silver-soldered (rather than lead) for longer lamp life.  This lamp is sold under Bausch & Lomb part numbers 31-31-75, 31-31-76, 31-01-05, 31-31-42 and others.