I am looking for information on a Dutch oil painter named J or T Maas?
 He may be very obscure.  I have a painting of a Dutch landscape by
him that is at least 60 years old.

Unfortunately for you, Maas is a very common Dutch surname; the
initials T and J are also of course very common; and many, many people
paint landscapes. So even if you obtain information on a painter
called T or J Maas of about 60 years ago, he or she might not be the
painter of your picture.