Palma Real Golf - Who is a local?

We, three of us who live much of the year in Troncones and golf regularly, went to golf at Palma Real for the first time this year. With our Permanent Resident cards we asked for the local discount (1200 pesos vs 1600 pesos). They denied us. Apparently one must have a Zihuatanejo ID card for the discount. There was literally no one playing golf. Between the three of us there were decades of living here and golfing here. Pretty lousy policy. Hopefully they will rethink this one.

It begs the question- what is a 'Zihuatanejo ID card'?
Is it something like a 'Voter Registration' card- which I believe I was asked for when I tried to sign up for Mercado Libre.