Yep, looks like an aluminum alloy body. My dad had one similar to that growing up. We took that camping many times. Best grill we ever had to date! The lid finally got a crack in it and broke years ago. We tried to replace it, but as luck would have it, learned that model was no longer made!
Actually, it is cast iron and this rickedy ole thing has been around a long time. Hard to find cast iron grills anymore here in Canada as, like you say, most are aluminum alloy. This grill cooks the most meats ever as we have used smoker chips which bring out a wicked taste in everything