क्त-suffixed or अनञ्-suffixed सुबन्त combined with नञ्विशिष्ट (i.e. where नञ् is remnant and prominent) समानाधिकरण सुबन्त have तत्पुरुष status. For example, कृताकृत (done or done, it's the same) - where कृत is without नञ् while अकृत is with नञ् (i.e. नञ्विशिष्ट since instead of कृत नञ् carries the key meaning).