Nice Mac-90. You may not realize it, but you have a true military battle weapon. That is a real AK, not the ones sold today. The only true AK's were imported pre-'98 into the USA. They were all made in military arsenals by military personnel and built to military spec. And they were built by com-bloc nations.
AK's or kits imported today cannot compare. They are either commercial quality or they are put together by weekend warrior "gunsmiths". The best AK's were the PolyTech Legends, Egyptian MAADI's, Norinco's, MAK-90's like yours. Don't even waste your time buying an AK built in America. They do not have the ruggedness and can also jam when your life depends on it. Even the ones imported today are not imported to standard AK spec. They have to all be converted in some way to get them to resemble a true AK of the past like the ones I mentioned. Never sell that. But if I were you, I would return it back to original configuration. Here are more details:
PolyTech Legends - built by Chinese military
Egyptian MAADI - built by Egyptian military trained by Russians using Russian tooling
Norinco & MAK-90's built by Chinese military