I have seen this kind of mark on various cast metal parts. This is an image of the base casting of a hard disk drive made by HGST.

Markings on an HGST HDD base casting

  • What are these marks for?
  • What are they called?
  • $\begingroup$ Lego does something similar. Take a peek at the underside of a Lego piece (easiest to see with the plates). Every part appears to have some numeric designations with particular manufacturing-relevant meanings. As usual, SE has us covered: bricks.stackexchange.com/questions/1399/… $\endgroup$
    – wwarriner
    Dec 12 '17 at 22:17

these are part-tracking marks. they indicate which cavity in the mold the part was cast from, in which mold set, in what molding machine, in what year, month, day and shift. this way, a part that fails its finished goods inspection or failed in the field can be tracked backwards through the factory to its source, and the reason for the failure fixed.


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