It doesn't look like it opens like a trunk, though the bracing where it would open if it were a trunk buldges out more than it does by the hinges, so I have to take a closer look. It probably opens like an oven or a safe. If we assume the hinges should be on the side, then it's an inch taller than it is wide. If they should be on the bottom, then it's an inch wider than tall. Hopefully I'll be back there in a few days. I'll post when I have more information.
BTW, lots of people have seen it. There's old grafitti on it and two people came by in the hour or so I was there last time. There may have been concrete poured on it to stabilize it a little. It's in an undeveloped section of a large area that has various ball fields. Oh, WTH... it's in Calvert Vaux Park in Brooklyn. The city never replied to my e-mail, but if I discover it's a safe, there may be more interest.