If it was found in the streets, I'm not so sure, but if it was found at a shop or restaurant or something like that, it's probably worth letting the owners know and/or putting up a sign in the window. I'm not so sure of the legal precedent, but I think you're also supposed to report lost goods to the police, at least so that it's got an official ID number (or something like that).
But yeah, first of all, it's worth charging it and seeing what you can work out.