Ratings and what they mean for circuit protection
The 1.5KE27-E3/73: With a 21.8V standoff voltage, the device does not conduct at normal operating levels up to that rail; it starts breaking down at 24.3V minimum, ensuring the protected line stays below the clamp ceiling.
Sourcing reality for an obsolete part
Expect date-code spreads typical of end-of-life inventory — sealed reels or tape-and-box packaging as available. For new designs, a functionally equivalent TVS from the same TransZorb family with a similar standoff and clamp voltage should be selected — the axial DO-201 footprint remains common across the series.