Elphinstone is a "fateful" place for HH, " the secret terminus". and VN once explicitly connected this word to ivory ( besides Ivor and.Ivory) when he mentioned Quilty's dude ranch "at about a day's drive from Elephant (Elphinstone)."
He also wrote about "coruscating trifles as A vagabond in Italy by Percy Elphinstone, author of Venice Revisited, Boston, 1868"...
Alfred Appel Jr. in his note (31/3) wrote that "Elphinstone and his books are also genuine, according to Nabokov, though it has been impossible to document this. Nabokov recalled finding A Vagabond in Italy "in a hospital library, the nearest thing to a prison library. Later on he adds " for him the 'fairy tale' (...) ends in Elph's Sone, just as it had begun in the town of 'elf'."
While examining Borges's Norton Lectures I came across his praise of J.Joyce's masterful creation of the sentence "glittergates of elfinbone" in Finnegans Wake (1939), when Borges detailed the process of J. Joyce's metamorphosis of the German "Elfenbein" ( short for Elephantenbein ) into "Elfinbone".
I thought that perhaps VN had been referring to James Joyce when he mentioned Percy Elphinstone and "A vagabond in Italy". Alfred Appel's reproduction of VN's own words about having encountered a book bearing this title in a hospital library makes a lot of sense ( Elphinstone hospital, HH in a prison, etc), but I wonder if this book has been, finally, discovered or documented, or if VN might have playfully indicated Joyce by it ( but in that case, why Percy? ). I have not sufficient bibliographical information to ascertain that and I would welcome any indication about this issue.