The 1.5KE68-B: The 58.1V standoff means the diode does not conduct at normal operating voltages up to that level; it only begins to avalanche when the transient exceeds the minimum breakdown voltage of 61.2V.
Littelfuse lists the 1.5KE68-B as obsolete. A board-spin replacement may require re-qualifying the clamp voltage and package footprint — the DO-201 axial leaded form factor is common, but the electrical window (58.1V standoff, 96.6V clamp) is specific to this variant.
Temperature range and deployment context
The wide thermal margin means the diode's leakage and breakdown voltage shift within spec across the full temperature sweep — relevant for a circuit that must clamp reliably at cold start or under-hood soak. General-purpose application classification means it is not qualified to a specific automotive or aerospace standard — the temperature range is broad, but the part lacks AEC-Q101 or MIL-PRF-19500 screening. For hi-rel programs, a screened JAN or equivalent variant from the same family would be the correct call.