LP2989: marking faded issue for PN#LP2989AILD-3.3/NOPB (SO#422376)

Part Number: LP2989

Tool/software:

Hi Tech,

PN#LP2989AILD-3.3/NOPB

PO#029-C6268

QTY: 144

D/C: 2439+5 & Lot Code: 4215244EM4

Our customer received above parts and found all have marking faded issue.

Please see attached image for details.

They want to know what the cause is.

Is it normal phenomenon?

Thanks.