+1 For HFC. They're made in Taiwan. That's the most likely company. However there are other companies such as KJ Works, or KWA that are also in Taiwan. You'll be able to tell it's a KWA though since they're the OEM manufacturer for KSC.
Ho Feng Corp (HFC)
http://www.hofeng.com/eng/
Check it out, I didn't find the exact gun but if you look on page 5 of the gas pistol page you'll see something that looks quite similar to what you have.