Yes, DD is a forum / western name for the Dandong 4130 which was originally used by noob. The problem is that “SA” just means “super Asian” and sone of the slim 7750 movements were labeled as SA4130. The DD prefix is less ambiguous at the cost of being less universal. However some of the better TDs (eg
@CTime ) have been good about using the DD prefix to identify movements like the DD3285 and DD4130.
As I wrote in the “naming conventions” section of my guide (linked above), movement names are a shit show. Don’t rely on what’s written on a website. Learn to ID movements based on the labeled pictures provided in the guide.
I have a strong preference for labeling movements with a prefix from their manufacturer, eg SH for Shanghai movement factory, DD for Dangdong, and HZ for Hangzhou. But there is the complication of there being multiple movement factories in Shanghai: “Shanghai watch factory”, “Shanghai Jinghe industrial Co.”, and “Shanghai ZuanShi watch factory”.
My understanding is that the movements we call often prefix with VR or SH (eg the vr3135, vr3235, sh3285, sh4130) all come from the Shanghai Jinghe industrial Co. but I could be wrong. Perhaps
@CTime can set the record straight.