When working on anything that is repetitive, it is important to break up the design. It is just more interesting to have some variety within the pieces that make up the whole. To make sense of this jumble of links, I concentrated on the larger pieces first and used their shapes and their relationship/distance/size to each other. By making sure that the most obvious pieces are recognizable, the piece will take on the form of the reference photo.
The medallion has been a bit challenging because of the small size of the chain links. After trying varies ways to accomplish this, I decided to keep the mid brown underpainting and to use a method similar to erasing out. For this purpose I have used a very old mini brush (almost worn down to the ferule), which I dipped into solvent and basically scratched out the lightest links. Then using my pen again, I reemphasized the darks. This seems to work and the chains are slowly taking form.
As I work on the light parts I also have to keep in mind that the delineation of form gets often lost. In other words, some areas are not as finely defined as in the mid tones.