advice needed, tricky one.

Ive been asked to reproduce a photo framed about 100 years ago with glass, that im not allowed to remove. what lighting do i need to use to not get reflections, ive tried everything, the problem is the glass has mould behind it and just cant stop the refected surface, any advice would be great.

cheers don

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Pentax K7, Panasonic fz150, Olympus XZ1, my main toys.