That's a pretty unique looking snare. I've never seen a throw off or tension rods like that before. I used to have a Sonor kit. It came with a double ended drum key. One end was standard and the other end looked like it might fit those T-rods on your snare. I could never figure out what that end was for. Anyway, cool looking drum. Cool1

Sonor used slotted rods for a long time. I have one of the keys you describe. Unfortunately non of my recent Sonor slotted keys fits this old snare very well. I need to find a 60's slotted key to get a better fit.