This query finds cultivars marked as fertile either as "seed", "pollen", "both seed and pollen", or those marked as "usually sterile".
Daffodils are fertile when the number of the chromosome sets can be divided by two and this gives a whole number. There are exceptions and mismatched chromosomes have occasionally produced offspring.
You can also estimate fertility of pollen by observing the amount of pollen on the potential parent bloom. Theo Sanders of Germany has done an extensive study of pollen volume and chromosome content of daffodils. This study and others, including one about the possibilities of hybridizing, are available on Theo's site theo-sanders-daffodils.de.
Brian Duncan of Northern Ireland has hybridized thousands of cultivars in the past thirty years. During a visit by some of our ADS members, he stated that a good rule of thumb is to assume that daffodils are fertile.
People generally have more success matching daffodils from similar classes.