In this post you can see all types of markings that were used by Soviet factories that produced binoculars before 1945, and period when they were used.
Originally this table was created by Russian collector Pavlov V.I., but table was in russian, and was not widely known. I transletd some information and edited it a little. Original table contained some information that will be not understandable to inexperienced binoculars collector, so I removed it.
You can download original table by link below