Non-ECR category for an Indian Passport, without birth certificate, class 10 cert. and tax returns

I am applying for a new Indian Passport for my dad. Since he is above 50, the website is taking Non-ECR category by default.

The problem is my dad does not have the following documents:

  1. No birth certificate
  2. Although he has passed class 10, we do not have a class 10
    certificate. The school was in our village and is probably closed
  3. He has a PAN card and it has the correct birthdate, but he has been
    retired (business) from quite sometime now. We do not have any
    Income tax return file or anything.

What else can be used to prove Non-ECR category?