A visitor to the auction viewing sent the following:

I did a bit of research for you on lot 93. I couldn't discover who the painter was (the signature is in Russian, I think it is Vishenvsky, but it is hard to decipher), however I believe it to be a scene of the attack on polish troops in the city "White Church" (Belaya Tserkov') in the Ukraine in 1920. The man on the white horse was the famous Soviet military leader Grigory Kotovsky (http://en.wikipedia.org/wiki/GrigoryKotovsky). There is a painting from 1960 by the Russian artist Poplavski Mikhail Konstantinovich showing the same comander (http://www.farfor-town.ru/109--), as well as some other artworks depicting him: http://varvar.ru/arhiv/slovo/kotovskiy.html http://www.hobobo.ru/media/diafilm/item/grigoriy-kotovskiy