This is most likely the Heisey #1 Madonna that was made as a reproduction fundraiser. The D is for Dalzell Viking who made the piece for the Heisey Collectors of America to raise funds to sustain the National Heisey Glass Museum.
The museum may be able to help you. Unless it was made for a special event I doubt it's Heisey. Heisey has a diamond with an H in the middle.
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