I suspect they used Wipe New- Comes in the pouch on a white towellete saturated in it. I've used wipe new extensively, and with good prep work your lights can come out look brand spankin new. I've got to redo my headlights sometime, I pushed too hard with the Wipe New and let streaks/ drips on my headlight. I might try to just wetsand and polish the wipe new coating itself to try to level it out.
This is an example of wetsanding +wipenew. This is my 1984 Honda V65 Sabre- stored outdoors in the sun for the most part. I realized after winter storage (4 motnhs of which were outdoors) I couldnt see my gauges at all. The RIGHT side has NOT been sanded yet, that's the "before" picture.
And after wet sanding 1000, 2000, and 3000 grit, plus wiping wiht the Wipe New cloth.
Taking the gauges apart was too risky, as the clusters in decent shape are SUPER rare, and the trim to it is very fragile. I decided to go for it, because it was so bad that I simply couldnt have made it worse. I needed to be able to see my gauges!
They still look brand new, shiny and smooth, 5 months after treatment, and it's been stored uncovered in the sun 100% of the time.