细节
Three spoked discs with single spirals
of thirty round holes, aluminium, painted black -- 16 in. (40.5 cm.) diam., centre holes 9/16 in. (9 mm.) (3)
of thirty round holes, aluminium, painted black -- 16 in. (40.5 cm.) diam., centre holes 9/16 in. (9 mm.) (3)