Normally hat package was a diode or transistor, led's in this generation did not use the ceramic and epoxy fill package, but used a modified TO18 package with a glass top to allow light out. Very likely a transistor that has had the absolute snot blown out of it, but the case did not shatter. But a better image is needed, especially of where it goes on the board.
Looking at the board and the front that screams old Fluke, it probably is a reference diode, likely 6V8, either a simple temperature compensated zener, thus the looking like a capacitor, because there are 2 compensation diodes in the package, or a speciial Fluke zener, which is pretty much the same.