That's a Warren & Sweat, although I can't tell you the model name, if it even has one. The company has been out of business for quite some time now.
I picked up the same stand, except that mine has an open front, along with one of their loc-ons, about 13 years ago.
Even back then, it seemed that sellers were liquidating their remaining stock of Warren & Sweat.
Mine came without instructions also, and I'm sorry to tell you that I was never able to find a manual, even after I searched the web. Maybe somebody else here can come up with a source for you.
There really isn't much to using the stand, but I can tell you a couple of things that I found.
First, and I know this seems obvious, but be sure your pins slide down through the cable loops. I found that the pins can slide down through along side the loops, and not actually in the the loops.
The second thing is the foot strap. Pull plenty of slack through the cam buckle, and then pull the strap on each side of the center slot up enough to get your feet in.
I just tighten the strap down on my toes from there, but I suppose you could run the strap behind your heels for a more secure fit.
In your picture, I see the foot strap is up over the side brace near the pin, when it should be under that brace and under the foot rest. It should come across right from the side slots so it's easier to slide.
The base is really solid, but the hand climber can fall some when bumped if you don't have a strap around it and the tree, to hold it in place.
I put the buckle on the bottom. I noticed when I was taking it down last night the pins can be a little hairy to put back in so as long as your careful should be ok.
I'm impressed with its overall grip to the tree. The top platform isn't as stable as the summit at least not on the smaller pine I had it in last night. I'll definitely put a strap on the top, make a paracord umbilical cord and retrieve rope.