i think the translation would be better with "part" instead of "piece" . I'm sure there is another word for "part" in Romanian, but still.....
"parte" may be your word here, because that Romanian word for "piece" is generally reserved for "electronics/mechanics" - I do believe. . . Oh, nahautl1939, that is so sad about the museum in Rio de Janierio.
Why not "this is a piece of the telephone" Is "a" here a preposition which can mean of or from? Elsewhere i have seen it explained it is simply a part of the possessive needed if the word immediately preceding the genitive noun isn't the thing possessed? Confused.com.
PS Your link doesn't work for me, but I think "este a" (a fi a) belongs together. French: "Il est à moi" = It belongs to me, literally "It is to me" = It is mine. "To be someones" is a fixed expression, too.
Confused.com is just a joke not a link! I get 'il est à qqchose' but that isn't followed by a word that already contains the possessive. I find this Romanian structure is like saying 'it is to mine' rather than it is of / to me. In some circumstances we get this extra 'a' others not leaving me confused. confused.com find a good quote from insurers - they are a 'screen scraper' in that they take the data you give them and use it on lots of insurers websites to see what prices they get and show you them in order of price.