In the Netherlands it is generally used to indicate that something has been done correctly, like a check.
I would like to know the unicode and/or the name.
I'd say the name is 'Approval curl' and there is no unicode.
In The Netherlands the naming differs, so there should be differnt English words too if English speakers would use the symbol I guess. But if I had to choose, Â´approval curlÂ´ would be my choice.
The appearance of the sign also differs too. See here a printscreen of two slighlty different 'krullen' (the Dutch plural of 'krul'). I copied those from 'www.goeievraag.nl/maatschappij/onderwijs/vraag/85664/teken-genoemd-vooral-scholen-gebruikt'.
Some of the Dutch naming I found on the internet: vink(je), krul(letje), paraafje, slingertje, goedje, plusje, puntje, bonusje. See also here the comment made by madelief2100.
Some additional info for non-Dutch residents: The usage is comparable with the checkmark. I've seen it used by teachers to state something is done, done correctly or done good. When I went to high school (that is around your 13th year of age) I haven't seen it used by teachers anymore. I assume it has some childish connotation to it.