Thanks! The other side is the front/omote showing Shinra Saburo playing a Sho on top of a mountain underneath a silver moon and clouds and above golden fog. It's by Nomura Katsumori(1835-1917, he signed on the front like most Natsuo School peeps), a student of Kano Natsuo and teacher to Kagawa Katsuhiro. From the mid Meiji era onwards he worked mostly for the Imperial Household Agency so his works are quite rare. I'm going to post a new thread about this tsuba some time later