To the best of my knowledge, there are three categories of these notices.
Code 1- 10 fingers prints
Code 2 - Index fingerprint, Photograph, signature
Code 3 - 10 fingers prints, Photograph, signature.
Code 2 is usually issued when your 485 case is ready for adjudication.
Code 3 is usually issued when your 485 case is ready for adjudication but your fingerprints probably have expired.
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note: I am not a lawyer, please verify information with competent authority