blau
3505
The Ellipse is the odd one out, because all the rest are round.
The 5196 is the odd one out, because all the rest have indices rather than arabics.
The 6119 is the odd one out, because all the others have smooth bezels.
The 3445 is the odd one out, because all the others are modern rather than vintage.
The 5227 is the odd one out, because all the rest have regular rather than hinged case backs.