This Nikkor 28mm f/2.8 with serial number 546286 falls into the late-1970s production period. Based on Nikon’s numbering and the MIR historical records, it is most likely the AI version made between 1977 and 1981, which carried forward the 7-element design of the earlier non-AI “K” lens (1974–77) but added the AI coupling ridge for compatibility with newer Nikon bodies. This version predates the 1981 AI-S redesign with Close-Range Correction, making it a classic compact wide-angle from Nikon’s manual-focus era.