2210 - I like that better than my first idea. A counterweight rolling on an inclined plane in greased tracks. If the weight is 1500 pounds and the thing to be lifted (perhaps a gate) weighs 500, it will balance with an incline of 19.5 degrees. You need only to overcome friction to raise or lower the gate.
I imagine it would roll in greased grooves and the cable would be attached to a greased fitting over the red bulge. The hole might be for automatic lubrication.
I see several advantages compared to a hanging counterweight.
1. It's out of the way.
2. Behind the normal range of motion, the tracks could curve up to arrest the motion of the weight instead of letting it crash into anything if the cable breaks.
3. The cable would bend 110 degrees instead of 180, meaning, with a given pulley diameter, less friction loss, less cable wear, and less strain on the pulley.
4. More inertia than a 500-pound hanging weight, so that it will move slowly and if the worker gets the gate moving, it will tend to open or close all the way.
5. Easier and safer to service than a hanging weight.
If it was attached to a fire escape and slightly overbalanced the weight of the ladder, the ladder would swing down fairly slowly when somebody descended. A "dip" at the top of the inclined plane would hold the counterweight so that once down, the ladder would stay down.