How to tell the TK and HY lens apart for Thunder Laser Aurora Galvo Heads

HY Lens are marked similarly but without a serial number on the lower brim.

There is a way to tell whether it is K9 glass for 20-50w fiber or Half Berylium type for 60-100W fiber: on the Half Berylium lenses there is an additional label of FSB.

Please check the screenshot in attachment, an example of HY F160 lens of different types. Hope this helps.