Some razors I have seen on eBAy are described as having a barbers notch, refering to the cresent cut out at the end of the blade between the cutting edge and spine.
These were traditionally associated with barber's razors. The notch reduces the weight of the razor, and theoretically allows you to shave the bit just under the nose a little easier. I've got several razors with that notch, and never noticed any real difference one way or another, but then I'm not a barber.