The Thor drill I picked up recently, is about that size... Somewhat ironically, I use it exclusively for drilling smaller holes in steel... Why such a big drill for little holes? Well, the weight of it is perfect :P All I have to do is hold it upright, and its own mass will feed the bit just about perfectly. I will only use small bits with it, though. So if the bit gets stuck, it will be the thing to break instead of my arm... It does drill steel REALLY nice though. It's geared just right for it.
Can't help you much with info on the drill itself though. I have a handful of Skil tools that look like they have the same sticker on them, so probably the same era as yours. And mine, like yours, were my grandfather's.
I would guess the chuck is original, though.