... some time ago by mail: "Ci" Meaning "Codigo de Inventario" (Inventory code used in internal control of the Argentina Navy stores).
As you know in the past many "experts" were telling that those intials corresponded to different Military Corps, something I was sure was wrong.
By the way, I never viewed in the flesh an ARA marked watch here. Suspect that most survived examples are gone to USA or Europe.
May be some very few remain here in hands of desendants of military members who were issues with them. Who knows.
A very interesting aspect that has been haunting me for many years.
Abrazos amigo Nicolas! Abel