Serial numbers HUH? Please help me!

I'm trying to insure all my gear and I cannot work out which number is the serial number on the lenses. I think I'm right with the camera, I'm assuming it's the number underneath the body but the lenses, I am not sure about. There's a number on the 100m macro but it doesn't correspond with any on the box it came in, and there's so many numbers!
Same with the 70-200mm is the manufacture date number starting with UX classed as its serial number, or is that something else.
There's no number at all on the 50mm 1.4 but there's 4 to choose from on the box. Do I just close my eyes and point a finger and see where it lands?

You should find it in a couple of different places on the lenses, on my primes its on the outer lens body near the lens mount in white. On the L zoom it's on the metal lens mount itself. On the 50mm it's engraved into the black central section of the lens mount (8 digits)

The date code is not the serial no.

Thanks, I've found them all but the 50mm didn't have anything on it.

Who are you insuring your gear with?