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If I'm looking in the correct area of the 1975 Oldsmobile Parts Catalog two (OEM) part numbers are mentioned - one specific to model year 1968 the other 1969 - 1973.
That's the plastic timing tab used on late 1970s-up Olds motors. It "looks cast" because it is - cast out of plastic. Note that yours also has the round feature for accepting the Kent-Moore Mag-Tac probe.