Is it possible to tell if someone is on Facebook mobile or PC?

[Jim]

On Facebook chat, is it possible to tell whether a person is online on their mobile or on their computer if they just have the green dot next to their name?

And if so how can you tell?

Thanks

[Jacob]

If you send a message to some it will return with "Sent from Mobile" or sometimes there's a symbol where their online green dot should be, but other times there's no way of telling.