Saskia (Heindrickje Stoffels) after Rembrandt. Of the several Rembrandts I could have copied, I felt that this one was most within my technical means. It worked out successfully and I am still fond of it.
If you consider which is better, hanging a printed lithograph or an oil painting, there isn't much comparison.
On the other hand, I recently went back and looked at the original and this bears little resemblance. I am a better draftsman now.