The Legacy has a faceted endcap like the PFM did on the Touchdown filler. The Legacy II has a smooth rounded conic endcap and the Legacy Heritage has no touchdown filler. Also the Legacy used the three prong clutch closure while the Legacy 2 and Heritage use a full clutch ring.
Remember that things moved as transitionals so I doubt Sheaffer stopped using the three prong closure until they ran out of them so finding one on a Legacy 2 would not surprise me.
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