John Deere backhoe- What am I?

My friend bought some property and this backhoe may be left behind since it is not running. I've never seen a John Deere 310 backhoe that slides on a rail and I can't find one like it with an internet search. How does it move back and forth horizontally? I did not find a rack and pinion system or any obvious way to move it back and forth. Any guess as to the year of the machine? I think the only thing of value may be the Amulet mechanical thumb.

Steve

European version. Side shifters are the norm across the big pond.
Deere offered both versions.

Ed

I owned one on a 410 chassis. The hoe is clamped to the bar by hydraulic pressure. Somewhere on the valve tower there will be a very short stubby lever that rotates, when it is straight out it releases the pressure on the bar. Then you swing the boom left or right and push/slide the boom hub to the desired location. They're good for digging next to foundations and you can dig a rectangular hole for a septic tank without moving the machine. Swing is a hydraulic motor instead of cylinders and is somewhat weaker. The stabilizers are a little less stabilizing too. I had mine for about 15 years and did a tremendous amount of work with it.

Good set of recaps on the back of her. They might come apart if she's been sitting long.

Are these considered rare in the US? Would most buyers want to stay away from them?
I finally found it on the JD parts website. It's called a 9500 series backhoe.
https://partscatalog.deere.com/jdrc/sidebyside/equipment/68895/referrer/navigation/pgId/165959

Good observation on the tires cutting edge.