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The mark on the flower and the leaves are close to nivalis so I think it must be a nivalis or a nivalis hybrid. If it ever was a named cultivar then I don't see enough distinguishing features to re-identify it if the name has been lost. But most snowdrops from friends are exactly that and not named cultivars.
Blonde Ingrid's 'Cowhouse Green' is also looking good. That one doesn't seem to be so difficult to get -green (-ish) snowdrop.