I worked for Dynamic Equipment. The attachment you have was called by Dynamic by the name "Mininip" (mini manipulator). The company has apparently been inactive for several years. An unsuccessful attempt was made to purchase the engineering information. It is not clear what happened to the records when the office building was sold and remodeled. As I recall, the hydraulic circuit is fairly straightforward. Typical mobile hydraulic valves were used with the lift truck hoist and side shift hydraulic system. You might try consulting a hydraulic engineer or a hydraulic system integrator. They can trace the circuit for you. In general, the accumulator is kept precharged to 200 PSI above the system pressure, which I think was 1500 PSI. Carlton Forge in Paramount, CA, may have a similar machine. You could also check with used equipment dealers, who might have one with a schematic drawing. The manual information generally consisted of arrangement drawings and a replaceable parts list.