I have nothing about that book, but the dismissal of catechumens was treated by Jungmann in his The Mass of the Roman Rite, volume I, p. 479 (PDF available on-line).

He writes that in the cathedrals, until the end of the Middle Ages, the deacon cried after the scrutinies: "Catechumeni recedant. Si quis catechumenus est recedat. Omnes catechumeni exeant foras." ("Let the catechumens depart; if there is any catechumen, let him depart. Let all catechumens go out.")

https://archive.org/details/ephemerideslitu02unkngoog

It's a journal and surely some Catholic seminaries and universities have back issues. I didn't try searching through this link to see if I could spot vol 53.

Looks like it's just 1-12. I'll try the seminary suggestion.

Cool!