7 Agricultural Machines, namely, [ silage cutters, silage unloaders, ] silage unloader feeders, fodder mixer feeders, [ bale feeders, ] silage feeders, [ straw blowers, ] manure spreaders, [ and fertilizer spreaders; earth-working machines, namely, harrows, power tillers, plows, cultivators, and pulverizers; haymaking machines, namely, tedders, windrowers, combined tedder-windrowers, rakes, swath-groupers, grass mowers, grass mower-conditioners, and grass aerating mowers; harvesting machines, namely, harvesters and forage balers; treating machines, namely, sprayers, power seed drills, pneumatic seed drills, and mechanical seed drills; machines, namely, grinders, scrub cleaners, shredders, ] and structural parts therefore