Website says it's steel. The tubing seems rather thick. It's probably pretty heavy, especially with those deep rims.
The GT GTB, imo, is a great aluminum frame. Can't speak for the Gutterball though.
How much are you picking this up for? There are a lot of other more popular off-the-peg options, even here in Toronto.
Also pay us a visit at
www.tofixed.com.