Hello cowboyinvest,
There is no valid retail 3-pc license for Office 2010 Professional. Retail licenses for Office 2010 professional allow installation on up to two licensed devices---one being the primary license-holder's main computer (usually but not always a desktop)
and the other being the primary license-holder's portable (aka laptop) computer.
There is a valid retail 3-pc license for Office 2010 Home and Student. All three installed PCs must be in the same household, and the installed product cannot be used for commerical, nonprofit, or revenue generating activity.
I see the incorrect reference to 3 pc licenses on suspicious eBay and Amazon marketplace listings all the time. Best advice: do NOT expect genuine Microsoft product when purchasing from eBay sellers or Amazon marketplace sellers.