Aliosha asked me to help him with his great-grandfather's photo. Here it is:
And here's Major-General Stepan Alexeyevich Boldyrev's service record, dated 1907 - when the above photo was taken:
At that time, Boldyrev was commanding 1st brigade, 2nd Don Cossack cavalry division. Born in 1852, he was educated in Imperial Law School in St.-Petersburg and in Novocherkassk Cossack Cavalry School. Upon graduation, he enlisted in Life-Guards Atamansky Cossack regiment.
In the course of his service, he held various military administration posts, until being appointed, in 1900, commander of 9th Don Cossack regiment and in 1904, commander of 1st brigade, 2nd Don Cossack cavalry division. He was promoted to Major-General in 1904 and awarded St. Stanislav 1st class in 1907. The photo was probably taken on that occasion. His other awards include St. Vladimir 3rd and 4th class, St. Anna 2nd class and a usual set of lesser orders and medals.
As Aliosha wrote me, Stepan Alexeyevich Boldyrev retired in 1911, stayed in Russia after the revolution and was executed in 1923.