I think this mean the whole black engine good silver engine bad thing is a load of ****
there must be date when the silver engine was updated and then refined as a black engine
so this means later silver engines are just good as early black ones
also if your bike is registered on a particular year doesn't mean it was made that year could of sat in a dealer for a year or two before it was registered
there must be an engine number at which things changed someone at Triumph must know this information ...they might also know who was on the grassy knoll in November 63