Late 1930's Houdialle factory service manuals call for them to be painted "M-1713 Air Dry Black Enamel" FWIW, M-1713 corresponds with Ford chassis paint (V8 era).
Model A era shocks were most likely sprayed with asphaltum-based enamel and would have a gloss level similar to wishbones and axles. Marco's website (
www.abarnyard.com) features a photo of a chassis on the assembly line with painted shock bodies (approximately similar in sheen to the wishbones/axles) and unpainted shock arms. It is likely that the shock arms would have been sprayed with pyroxylin (nitrocellulose) on the line during touch-ups, so the shock bodies would also probably have some overspray from that process.
I spent many hours filling and blocking my shock bodies trying to make them 'perfect'. They're not quite as glossy as the photo illustrates, but the black color is a spot-on match for contemporary Ford black asphaltum enamel (not all 'blacks' are 'black'). Oh, and the shaft should definitely be masked off...
