The Russian (previously Soviet) combat optic development efforts are probably the most diverse, unique and interesting in the world. As a result of having such a wide variety of ideas, with a lot of experimentation and R&D, Russian optics encompass some of the worst and the best designs on the market.
The Obzor 1P63/PK1 is one of the more modern Russian optics that can be acquired on the open market and it has seen service in very recent conflicts. It uses no batteries, leveraging either ambient light or a tritium bulb in low light, and has a reticle that changes based on light conditions.
Karl used this optic in a 2G-ACM match as part of the testing process. That video is here: