What is "Client Character Set" in bpimagelist

What is "Client Character Set" in bpimagelist?

I created an OpsCenter SQL report that shows me all the images that were NOT duplicated for the previous week.  I have a few images every week that keep showing up even though I know they were duped and bpimagelist shows they were.  The only difference from images that show up as NOT dupe and ones that show correctly is a field in bpimagelist called "Client Character Set".

The images that show up but shouldn't, have this field marked as "1"

Example:   Client Character Set:     1

The images that do not show up, working as intended have the field marked with a "12"

Example:   Client Character Set:     12

Any help would be greatly appreciated as I can't find anything on what this is.