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When thieves steal a painting by cutting it out of the frame, what does the gallery do with the bit of painting that remains with the frame?(r/AskHistorians)
I don’t know about later reattaching, but the fragments left after a painting is cut out of a frame are saved to confirm authenticity should the painting be found. Rewards for stolen paintings encourage forgeries. If brushstroke, etc don’t line up with the remainder it’s easy to confirm forgery.