Hello.
I’m composing a score in which I’m using Portuguese names for the instruments. I believe that, in English, the convention of using a period when the abbreviation is not the last letter of the word is used. The same convention can be used in Portuguese (at least, Portuguese from Portugal). However, I’ve observed that translated abbreviations only include the period if that’s the case in the English name for that instrument, even if it’s not the last letter in the translated name.
For instance, the Horn abbreviates as Hn in English, and “Trompa” is set to “Tr”, even if it should have a period (I would abbreviate as “Tpa”, by the way to avoid confusion with other instruments, which, incidentally, uses the last letter of the name, but I digress). The same happens with Violin, which is “Violino” in Portuguese and should be “Vln.” and not “Vln”, or Guitar (Guitarra).
I couldn’t find an example of the opposite (a dot in Portuguese when it shouldn’t), and no one comes to mind. But I’ve encountered some odd choices of abbreviations and some wrong translations. For instance, Accordion should be “Acordeão”, and I would abbreviate as “Acord.” or something similar (It’s Acordeon, abbreviated “Acorde.”). Hurdy-gurdy is not translated, and should be “Sanfona”. I don’t believe any of these are correct in any variant of Portuguese.