All records were cleaned first manually with microfiber brush + cleaning solutions then 30 minutes in a ultrasonic record cleaner.

Then I dried them on a record rack and listened to them all,  to make sure I was able to capture all noises / distortions / other sound quality degradation, especially sibilances in the vocals. Audio equipment used for testing are Pro-Ject  turntable with Ortofon 2M Red Cart + Speedbox + Phono Box SE2 preamp, Denon AVR-1912 receiver and Wharfedale Crystal 30 floor standing speakers.

Then I graded them based on physical condition and my listening experiences. As mentioned, the grading can be seen at top left corner. Grading is based on the lower one of the 2 sides, if side A is spotless as NM but side B is a bit worn as VG, I will mark it as VG.