With the heater blown, the LM399 could still be used at room temperature. So its more like an LM129 now, an unheated burried zener reference chip in a hermetic case. Depending on how high the TC is this might be still rather useful, or hardly useful.
The blown heater side might still work as a kind of temperature sensor, depending on how it is broken.
With 15 V in reverse the LT1001 might still work, but one does not no for sure how well it is working now. So usually one would replace it. Even if it still works like an OP the properties might not be as good as a new one and chances for failure are higher.