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A general description is here.
iconv() was incorrectly identifying R running in an Eastern European locale as using ISO-8859-2 (aka Latin-2) rather than CP1250: they differ in the positions of some characters, notably s and z with caron. This was seen in tcltk output from Rcmdr in 2.7.x, but might have occurred elsewhere (and earlier).
This also affected localeToCharset() which incorrectly returned "ISO8859-2".
The same issue seems to have caused problems with starting R 2.7.x in the Chinese (Hong Kong S.A.R.) locale on some systems (e.g. PR#12658): the problems were with locale names which contained periods.