The Tamron SP 90 mm f/ 2.5 Adaptall-2 model 52BB is a telephoto prime macro lens for 35 mm SLR cameras popular in the 1970-90s (via the interchangeable Adaptall-2 mount).
It makes it possible to take 1:2 macro scale pictures without teleconverters.
SP (Super Performance) - the lineup of Tamron best lenses.
This lens has replaced Model52B. The body design has been changed. Despite replacing some body elements with plastic, the build is still excellent, though inferior to the early version. A dedicated extension tube was manufactured for this model (for 1:1 macro scale).