That's a Garelick 4 step boarding ladder. You need to through-bolt the mounts for it into the deck. You may be able to see the mounts in the picture below, just behind the midship cleat.
I had the same ladder before, which eventually corroded. One leg broke when I was climbing it. In addition, the bottom step only reaches just below the waterline, so its not especially convenient to get out of the water.
So, I can't say its a great ladder.
The cheapest price I found was at Boater's World. It comes with the mounts.
http://www.boatersworld.com/product/366480051.htm
Storage is another problem. The ladder wont fit through the cockpit locker hatch.
A 3 step + 2 step folding ladder would be nice, if they make such a thing.