How to prepare bread flour to bake Soviet era breads that require "second grade flour"
(мука 2 сорта).
Soviet bread flours had different grades:
superior grade (similar to North American all-purpose flour, высший сорт)
I grade (similar to North American bread flour or somewhat darker and softer, первый сорт)
II grade (similar to North American first clear flour or artisanal flour of 85% extraction, второй сорт)
whole grain flour (обойная пшеничная мука)
The grades of flour are still the same in Russia and other former Soviet republics, but wheat quality has since changed, so flours have to be adjusted to the Soviet era levels, in order to bake with them using twentieth century recipes.
II grade flour from Russia corresponds both to French flours types 80-110 (82% extraction, 85% extraction) and to American first clear flour (75% extraction). Meaning its ash content varies (0.7-1.25% of dry matter) and its protein and gluten content varies (10-17% protein dmb, 24-35% gluten). It could be milled as straight flour of 85% extraction, or be a leftover flour during 78% extraction milling, what's left after patent flour streams were removed.