What does 'G' mean in 'The Adventure of The Red Circle' by Sir Arthur Conan Doyle?

There are these instances in the story where Sherlock Holmes is narrating some advertisements from the 'The Daily Gazette':

1) ‘Am making successful arrangements. Patience and prudence. The clouds will pass. G.’
2) ‘The path is clearing. If I find chance signal message remember code agreed—one A, two B, and so on. You will hear soon. G.’ 3) 'High red house with white stone facings. Third floor. Second window left. After dusk. G.’

What could the G here mean?