I couldn't find anything that shows the difference between the WC7556 and WC7556P. Typically the P just stands for printer. I would suggest calling into our sales department for more assistance @ 1-800-ASK-XEROX.
Thanks, TammyL-Xerox Community Manager
Be sure to click Kudos for those who have helped you. Select Accept as Solution for posts that have helped to solve your issue(s)!