It is reasonable to assume Chinese import because of the time the gun was made (based on seral number), the condition (major refinishing), and the mixed parts all say that. If the gun was not an China export/import you would expect matching parts and never refinished, since that reduced its value as a collector. These are guesses but very informed ones.
I expect the original caliber was 7.63, can you tell if the barrel was relined? Also check under the grips for rust and see if the grips have a number as well.
Can't say this enough, if you plan to shoot it (and I hope you do) be sure to replace the springs!