Distinguish muscovy duck eggs form eggs of other duck breeds

[cristiana shaw]

hi all, our muscovies just reached laying age and a new question has come up. how do we recognize their eggs from the eggs of our welsh harlequins and pekins? Since the muscovies are good mothers and their eggs take one extra week to incubate, I do not want to mix them up with the others, and possibly leave them in the nest for them to hatch. Does anyone have any experience with this?
Thanks!!!