The (negative) time delay exactly corresponds to one turn of the record at 33-and-a-third RPM; the pre-echo is muffled and a tad distorted, and only appears in one stereo channel (I forget which side). It's a cutting-time fault, caused by the wax for one turn being displaced slightly when the next turn is cut.

I've heard pre-echo on other records, but in this instance the quiet bits are so near silence that the break-through has the sore-thumb nature. Let's be charitable, and assume that the engineer was used to cutting rock-music records :-) .

PS: Thanks for the clarification, MudElf.