Neville's 1934 vision of fragmenting quartz and his meditating form
Date (happened)
1934
stated · preferred
Reasoning
Neville states the year of his own vision directly and without hedging; this is the happening date of the vision itself, and he restates the same year later in the same lecture (passage 538692, 'this happened to me in 1934'), so the two mentions are the same telling agreeing with itself, not independent corroboration but also no contradiction.
Told / reported
23 September 1968
estimated
Reasoning
The telling date is the lecture's own certain, doubly-corroborated delivery date.