In his letter to Annette Blagovo (a namesake of Anyuta Blagovo, a character in Chekhov's stroy My Life) Vadim compares his mental flaw to a missing pinkie:

Voilà. Sounds rather tame, doesn't it, en fait de démence, and, indeed, if I stop brooding over the thing, I decrease it to an insignificant flaw--the missing pinkie of a freak born with nine fingers. (2.7)

In the Russian original of Vadim's letter to Annette "pinkie" is almost certainly mizinchik. Mizinchikov is a character in Dostoevski's The Village of Stepanchikovo and its Inhabitants (1859), but Mizinchikov is also Onegin's neighbor in a discarded variant of Pushkin's Eugene Onegin (Four: XXXIII):

Madam Durin, of Pskov,

and with her one Mizinchikov. Eugene

perhaps despised the comments

or, what's more likely, did not know them

but, anyway, his habits

he did not change to satisfy them -

for which his fellows could not suffer him.

Mizinchikov: A comedy name, which, however, had its counterpart in the names of one of Pushkin's country neighbors, Palchikov, which comes from pal'chik, "fingerlet." Mizinchikov is derived from mizinchik, which is the diminutive of mizinets, the cuddy-finger (Yorkshire), the pinkie (Scotland), the curnie-wurnie, the minimus, the ear-finger, the auricular, Fr. l'auriculaire, so that the shocked gentleman is here "Mr. Earfingerlet." (EO Commentary, II, p. 459; In EO Index Mizinchikov is turned by VN into "Mr. Inch" or "Mr. Pinkie")

When I returned to Paris I found that my kind friend Stepan Ivanovich Stepanov, a prominent journalist of independent means (he was one of those very few lucky Russians who had happened to transfer themselves and their money abroad before the Bolshevik coup), had not only organized my second or third public reading (vecher, "evening," was the Russian term consecrated to that kind of performance) but wanted me to stay in one of the ten rooms of his spacious old-fashioned house (Avenue Koch? Roche? It abuts, or abutted, on the statue of a general whose name escapes me but surely lurks somewhere among my old notes). (2.1)

Stepanov - Stepanchikovo

Mizinov - Mizinchikov

Lika Mizinov (1870-1937) was a close friend of Chekhov's family (her surname does not necessarily come from mizinets). According to the writer's sister, Chekhov and Lika (milaya blondinochka, "dear blondie", as Chekhov calls her in one of his letters to her) were infatuated with each other. Iris Black (Vadim's first wife) mispronounces the title of Vadim's poem Vlyublyonnost' (Being in Love) as "Valley Blondies" (1.6).

There is Lika in Kalikakov, a Soviet "diplomat" whom Vadim caught using a hollow in a tree-trunk for his correspondence with another spy. Spying had been Vadim's clystère de Tchékhov (hobby, cf. violon d'Ingres)* even before he married Iris Black. (5.1)

During his incognito visit to Leningrad Vadim is accompanied by Oleg Orlov, a worthless poet whom Vadim had met in Paris before Oleg "decided to sell the bleak liberty of expatriation for the rosy mess of Soviet pottage." A. A. Orlov (1791-1840) was a writer whom Bulgarin and Grech attacked in their review The Northern Bee. According to Grech, Bulgarin in his little finger had more wits than all his rivals in their heads. To which Vyazemski replied: "pity he [Bulgarin] did not write only with his little finger." Pushkin is the author (under the pen name Feofilakt Kosichkin) of the article Neskol'ko slov o mizintse g. Bulgarina i o prochem (A Few Words about Mr. Bulgarin's Little Finger et Cetera, 1831).

*Chekhov is the author of Skripka Rotshilda (Rothschild's Fiddle, 1894).