Access to adjusting screw on Rear Brakes

Having trouble removing the rear drum on a 91 Cutlass Cierra. I cannot access the adjusting screw to back off the shoes.

( The ones I've worked on before ( GMs ) have a rubber seal in the backing plate which allows access to the adjusting screw ).

I see nothing in the backing plate or drum that can be removed to access the sjusting screw.

Manual says to drill a 7/16" hole in brake drum.

Any suggestions ?

Thanks,
Ronald