Assuming the voltage rating is the same, gear designed to work at 50 Hz will probably work even better at 60 Hz. At 50Hz, the transformer not handle as much power as it will at 60 Hz because the core runs into saturation (max current handling ability due to the mass of the core) earlier at lower frequencies.
Other than that, the only products that won't work properly at different frequencies are those that use the line frequency for timing. For example, older electric clocks and some electric motors are frequency dependent.
The other thing you should note is whether the product is specified to run at 117 volts (U.S. standard). Japan's AC power is typically 100 volts. I don't know what voltage is standard in China. Running 100 volt gear at 117 will cause the voltage regulators to dissipate more heat. That's fine for gear designed to work over the entire range, but check the specs.