To me, Muscovy ducklings just look like ducklings and I wouldn't be able to pick them out for the first couple of weeks.
But Runner ducklings should be very upright and lively. Muscovy ducks are close to horizontal in stance. So it should be extremely easy to tell which are which just by watching them move around.
Neither one of those is chocolate, so if you got runners, you didn't get chocolate runners. I think that is a rare color, so would have to be purchased from a specialist, not a hatchery.
But Runner ducklings should be very upright and lively. Muscovy ducks are close to horizontal in stance. So it should be extremely easy to tell which are which just by watching them move around.
Neither one of those is chocolate, so if you got runners, you didn't get chocolate runners. I think that is a rare color, so would have to be purchased from a specialist, not a hatchery.