trench binocular periscope question. is it worth it?

went to an antique shop today and found a trench periscope with tripod in the rubberized canvas case and carry strap. the case was well marked on both outside and inside. carry strap was intact and is in good condition. both case and strap were dirty. the "bug eye" type periscope had a right cloudy optic with grid in it. and the left optic was black. i think something had come loose on the inside. the brass painted tripod was present and is in very good condition with lots of black paint left. the optics were marked Nikko. there was probably a part missing from the optics as they rotated a full 180 degrees on each end. the seller has it priced at $300 is this a good deal? can they be fixed?

the pic below is of the same model type but not the same set. the one in the shop is a little more worn and is missing that locking knob.