In Casablanca, when Berger (Laszlo's Resistance contact) first approaches Lazlo, he pretends to be selling a ring. Lazlo doesn't realize who Berger is until he opens the ring and shows it to him.
After this, they discretely agree to meet later in the bar to talk about Lazlo's flight to Lisbon.
In the script,
Berger: Berger... At your service, sir.
Ilsa: (looking o.s., gives Lazlo a signal) Victor!
Lazlo: (to Berger, low voice, as he comprehends the signal) Meet me in a few minutes at the bar.
The scene is somewhat different, as Berger is the one to show the ring (which I assume to be the signal). However, what is this ring?
Is it some nazi-resistance symbol? Or is it just something random that they agreed beforehand, but without any specific meaning?