You can always tell when a valve stack has been working in the real world. Paint beat off, fittings changed, rust starting, oil everywhere, and still somebody was probably asking it to make one more job.
That is hydraulic equipment.
It will take a beating for a long time, but it will not forgive dirty oil, heat, bad seals, or worn internal parts forever.
A valve like this can look rough on the outside and still be repairable. The important part is what is going on inside. Are the spools free? Are the bores scored? Are the seals gone? Is it bypassing internally? Is contamination making it stick?
That is where the problem usually is.
We see a lot of these come in after the machine starts acting up. Slow functions, drifting cylinders, heat building up, or one section not responding right. By that point, the valve has usually been telling you something for a while.
Tear it down. Clean it right. Inspect it right. Fix what needs fixing.
That is how you get old equipment back to work.