A big hint is the single 8mm (12mm head) pinch bolt on the axle. That only existed on YZ250/400 D/E/F forks.
The way to tell between the three year models of forks, is to look at the underhang of the fork leg below the axle.
These are 250D forks:
http://i46.photobucket.com/albums/f128/annaandnathan/Bikestuff/Photo0158.jpgThe 250E forks have a second dummy dimple above the oil drain screw, and more underhang.
I'm pretty sure that 250F forks have a longer underhang than the D forks - VMX #33 or Google will be able to confirm.
These arre not IT forks. By the time the ITs got 38mm forks (1981), they had the seperate axle clamp plate that's held on by four 6mm studs.
So... I wouldn't be the house on it, but I reckon they're D forks.
An overall length measurement would help too.