I don't made a research but what I see on colored pictures is, that NGC 4657 is a part of NGC 4656 and most probable a result of the interaction with NGC 4631. The colors showed pink and blue tones which suggest star burst/formation.
For me it was always fun and challenge together to separate NGC 4657 into individual knots. With 16" I could pick up 4 knots within the hook and one more fainter knot 1' NW of NGC 4657. I don't try this with my 27" but I believe when the Seeing is steady enough NGC 4657 is extremely detailed. And no, I don't see the fainter extension to the NE.
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