I've carefully looked over datasheets for at least six processors and never noticed that section. [smiley=embarassed.gif] Thanks for the tip!
Ordering Code Package
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ATmega324PV-10PU 40P6
ATmega324P-20PU 40P6
Package Description
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40P6 40-pin, 0.600” Wide, Plastic Dual Inline Package (PDIP)
Even though the datasheet doesn't specifically indicate, this presumably is the footnote for "U"...
Pb-free packaging, complies to the European Directive for Restriction of Hazardous Substances (RoHS directive). Also Halide free and fully Green.