It's a walker 784/884, looks like maybe the unit was swapped out sometime in its lifetime or someone just repainted the frame. Might be money ahead, tearing the unit down prior to investing in a kit, just to make sure nothing is wrong internally. I see you started taking the handle bolts out, those bolts only hold the "inner handle guts" together, to remove the the unit you will need to disassemble at least one side of the frame.
If and when you need a rebuilt kit, give me a shout.. Any questions or concerns send me a PM as I don't always see every post.