Well I am striking out finding any DMD-1683 paint. I have searched online for a few hours and I have come up with the below equivalents. Figured I would update this post based on my research. Give people an option who have the Black BDM bikes and may need some touch paint, the below should get you close enough.
If anyone has any better reference and can dispute the below please feel free to let me know but this is to the best of my ability.
Apparrantly DMD-1683 and PPG 9700 are the same basecoat Black. DMD 1683 is just a "cheaper" version. The 9700 paint code is the one used on the cross reference for automobiles such as Ford, GM, etc. Therefore if you are able to order the 1683 direct from PPG it will be cheaper as it's not associated with a specific automobile.
DMD-1683 Equivalents:
PPG - 9700
Dupont = 99 & 99S
Ford Code = M3673 & M6018
GM = WA8555 & WA9333 & WA9303
Crysler = DT4014