Look at the shape of the plow. If the Fisher plow juts out towards the front in the center and tapers backward on both sides so that the plow takes a triangular shape, then it's likely an XtremeV Fisher plow.
Measure the height of the blade extending up from the bottom of the plow. Of the other series of Fisher plows, four models can be easily differentiated by finding the blade height dimensions. The HT Series Fisher plow has a blade height of 27 inches; the SD Series a blade height of 26 inches; Homesteader, 21 inches; the XBlade, 31 inches; and the MC Series, 34 inches. MC Series plows also use a reversible cutting edge which can increase the service life of the plow.
Note whether the Fisher plow has any expandable hydraulic arms which extend outward from the back of the plow. These expandable arms are included on the XLS Series, which can increase the blade width of the XLS Series Fisher plow from eight feet to ten feet.
If, at this point, you still haven't identified your Fisher plow, you likely own an HD Series plow. Like the HT Series, the bottom blade strip is yellow instead of black, but like the SD Series, a few of the metal support arms behind the plow travel up and are collected at a yellow, triangular-shaped support hold. (See References 2, picture for HD Series)