Compare to Agave americana. There are several sub-entries as well, though trying to attach a cultivar name would be a guess, at best, from one pic of a juvenile rosette. They grow in full sun in the ground here.:
http://garden.org/plants/searc...
The plain species entry doesn't indicate its' hardiness:
Agave (Agave americana)
Dave's Garden site is known for being a reliable source of hardiness info, and lists this plant as Z8 for the low end:
The bright window sounds good for winter, but your plant would love to be eased into as much direct sun as possible (gradually, over a few weeks so it doesn't burn) while it's warm outside, if that appeals to you & is an option for you.
