Some Oldsmobiles use a plastic timing indicator attached to the timing cover. It may have been broken off. I've seen it a bit on the core engines I buy.

 

timing marks

What year ?

 

its in my 74 cutlass

 

timing gauge location

1974 should be on the timing cover to the right and below water
pump 1976 and up have a timing gauge bracket including an eyelet for magnetic pick-up mounted straight up and below water pump. Shine flashlight downward behind the water pump to reveal gauge. If it is not present use a fully electronic timing
light