Anyone see these rotors before ?

Hey what's up FABO !
Changed my rotors because i had a strange wobble I was tracking down ,the process was straight forward but there was 4 holes in the hubs . I haven't seen this before .I'm no mechanic just keep my cars up to snuff myself but idk if these holes in the hub are the norm? . The replacements did not have these holes. Pic is attached .
Car is 1976 dodge dart with a slant 6 all stock minus the qa1 UCAs.

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