My UV-P-5 came with a lens preinstalled and another in a box. I have looked through the manual and can’t find which lens is for inner crystal engraving and which is for the surface engraving? The one preinstalled has the marking YD-355-50-F80-FS10 and the one in the box has 355-200-F290-D10Q
The F80 lens is designed for engraving on curved surfaces, while the other lenses are intended for flat engraving.