without being able to explain the bit of the motivation that isn't just daughterly interest

I covered by asking about my grandparents' possible pig club involvement with "I remember Nanna said that the street used to collect scraps for a pig"... (alas my remembrances did not ally with the full facts).

And I am of course mightily encouraged by such research... I trust that he pours forth inspirational and useful reminiscences.

ETA: Glad you made it across he country.