Timofei Kondratyevich Kvastsov
Kvastsov lives in apt. 11 at 302b Sadovaya. Koroviev impersonates him in Chapter 9 when he denounces Bosoi to the NKVD. Just to be on the safe side, they pick up Kvastsov as well.
Kvastsov's name comes from kvastsy, alum, the substance used in styptic pencils to disinfect cuts and stop bleeding.