The French seem very inconsistent about when they use M. for Monsieur. In the UK and US, the 'Mr', 'Madame' etc was dropped by about 1914.
Here http://www.russian-records.com/details.php?image_id=6128 they call N.P. Afonsky 'M N Afonsky' so the M is Monsieur again. Elsewhere they use M N P Afonsky. But they don't use it for the composer (G. Lwovsky) or for the main performer where the first name is given.
I think you and Kelly are both right! A.I. Labinsky could be Alexander I. Labinsky who was orchestra conductor for many records from the same time period.