A selection of Square card readers I've tested, from front to back:
Current production model (October 2010), Beta white (February 2010), Alpha black (Fall 2009), Alpha white (Summer 2009), Special red (Spring 2009).
I helped create the company by introducing its founders and recruiting their early engineers. I've been testing Square since it was Codename Squirrel in early 2009, as the twelfth user.
In the background: Square HQ, downtown San Francisco.