I measured the periodicity that I saw (looking like a little zipper) on the outer plasmalemmal membranes of two adjacent hepatocytes at a desmosome (green dots). They seemed to be spaced about 19nm apart, and were small (maybe 7 or 8 nm densities).  In addition the intercellular space in this desmosme really had a nice alternating linear look where the desmocollins and desmogleins would lie. Micrograph on the left, unretouched mouse hepatocytes and desmosome (mitochondrial tethered on the upper left, but somewhat inconspicuous), green dots, zipper densities, red spots, ribosomes, lines, likely to be intermediate filaments.