Investigating Iran's scientific proficiency reflected in its scholarly outputs indexed in SCI during the 21st century and 1980s, the present study tries to propose the use of three features of science production including Specialty Diversity, Specialty Stability, and the growth of publications in the specialties, as the primary criteria in evaluating the contribution sustainability of a science system at macro level. They can be seen as the prerequisites every science system should realize to ensure a sustainable movement towards scientific development. The results reveal that Iran's contributions had been not only limited in number in 1980s, but also exposed to serious subject fluctuations, so that a scarce number of the fields were found to be stable regarding Iranian contributions. Moreover, none of them had experienced a significant, exponential positive growth during the decade. The situation is incomparable to the 21st century where Iran's contributions were as diversified as almost all of the SCI subject categories. It also reached long- or short-term stability in a majority of the categories. None of the previously stabilized specialties collapsed in the second 6-year sub-period. On the other hand, previously fluctuating fields mostly stabilized later. Moreover, a majority of the fields experienced significant exponential growths. Overall, according to the results, a developing science system might be characterized by its Specialty Diversity and Stability, as well as an annual growth in its publications in the specialties. Though meeting the criteria does not necessarily guarantee the achievement of quality standards, it may enhance the visibility of the contributions and thereby their recognition.