Not a D, that used a detachable mag. Kind of hard to tell from pic but doesn't look like a M, that had a 16" barrel, referred to as a paratrooper model. Looks to me like one of the new production ones made in the 1980s and early 1990s for import into the US.
I'm all but certain that's a run-of-the-mill Type 56. The three Chinese characters behind the import mark indicate it's a Type 56. Also, the bayonet is a dead giveaway "M" variants had an unfinished lug that cannot accept a bayo. Yours was imported by KBI out of Harrisburg, PA. One neat thing about yours is that it was actually built by the devil - arsenal /666\. Nothing special about the gun, other than a less common arsenal (most imported Type 56 guns are from China's /26\ arsenal). But it is a cool conversation piece.
It's a nice looking shooter. Looks like a factory gun, but serial number(s) would help determine that, along with the estimated year the gun was produced.