In the book, Michael and Natasha, the house where supposedly Michael A lived with Natasha is identified as being on Nikolaevskaysa Street, 24 and appears to be a much smaller house than this one. According to the book, they lived here up through the revolution. There is a picture of it in the book. If I get a chance I will scan and post it. There is no mention of Uritskogo, 20a, although the book talks about Michael owning property on Baggout Street and wanting to rent another in Kseniinksy Street (this property is described by Michael in his diary : "The house has two floors, we're thinking of it for our servants.") Is it possible that one of these is now Uritskogo Street?
BobG