Actually, the number of pulses per revolution varies. On the casing of the E4P, 3 digits in the number are the pulses/revolution, ranging from 100 to 360. The bore will also be on there, so don't let that throw you off. for example:
http://ivan.blogs.chimerical.com.au/..._36_resize.jpg
The Pulses/Revolution on this encoder is 300, and the Bore is .157 inches.