Need magic that checks if a collumn contains values that CAN NOT be converted to Latin1

Hi,

I've got an 8.4.3 Unicode DB that accidentally holds a few records with
characters that can't be converted to Latin1 or 9 for output to CSV.

I'd just need a way to check if a collumn contains values that CAN NOT
be converted from Utf8 to Latin1 to select all those affected records.

I tried:
Select convert_to (my_column::text, 'LATIN1') from my_table;

It raises an error that says translated:
ERROR: character 0xe28093 in encoding »UTF8« has no equivalent in »LATIN1«
Regrettably it doesn't explain where it found this sign.

Select '\xe28093'
complains that this weren't a valid UTF8 code at all.
So how was it accepted and stored in the first place?

When I know which record has faulty content I can correct it.

regards
Andreas :)