The first SKS's to use AK mags were made by Midwest Ordanace in the USA. They were standard SKS rifles modified by them to use AK mags. The early ones done by them are easy to spot by the SKS mag catch.
Reps from China Jing An were brought to Midwest Ordanace to see the process they used to modify SKS rifles to use AK mags and also the mods done by Midwest Ordanace to SKS rifles to make the 16" barreled "Paratrooper" model. The first SKS rifle to use AK mags that was made in China was the "Sporter" model that was imported in 1988. It had a 20" barrel,the bolt was cut for stripper clip use,and a bayonet.
After the 1989 ban the "SKS-D" model which had a bar code sticker on the end of the box that had printed above the bar code "semiautomatic rifle, detachable magazine,SKS-D". There was not a model name marked on the rifle. The first ones imported in 1990 had the same stock as the Sporter model but no bayonet lug or bayonet. The ones imported later had thumbhole stocks and the bolt was not cut for stripper clip use. These rifles came with 16" or 20" barrels.
The last model imported was the "SKS-M" which had 16" barrels,no bayonet lug, the bolt was not cut for stripper clips,and a stock with a Monte Carlo cheek piece.