Poorly maintained sword ID

This sword was, in all likelihood, purchased either at a surplus shop or through a wholesaler shortly after the Korean War. It was given to me a couple years ago and I have tried my best to preserve it in the condition it is currently (poor) so as to avoid further degradation.
I have tried to match the markings on the tang to what is supplied on this site and others, but I am really not sure as to what i am even looking at to make the comparisons.
I am assuming it is a machine made blade (in fact I am hoping it is due to the poor condition) due to the markings that I think I am reading correctly and the other fittings that were attached.
Any information on the blade is appreciated as well as if there is anyway to "clean" the blade that would not cause any further damage.

Thank you