This type of fuse doesn't hold out until it blows at over current. Instead it will blow at a pre-determined temperature (as temperature is a better indicator) of imminent damage than a current regulated fuse.
Although it is the heat of high current that blows all fuses a clear explanation of Heat Actuated Fusing is in U.S.PAT.NO.5,097,247 here
Both of these resistors are from a DIAmuX AGM415 line card. The cards have failed and been sent for repair.
I am trying to source & procure these components. Qty needed: 5000.