Not easy to say. The absence of a blotch in the dorsal fin eliminates several "possible" species, and it might be Corydoras sodalis; I had this species back in the 1990's. There are today so many undescribed species being imported that it takes someone with a fair degree of familiarity with the family to identify. There are photos of every known/discovered species (described and awaiting description), over 160 now, on Planet Catfish if you want to search through them. Corydoras World has similar, but you need to be a member there.