Uno A Erre is a goldsmith and jewelry company based in Arezzo Italy.
Additionally, they either produce for or partnered with Gucci brand at some point between the 1970s-1990s. These pieces will be marked by both Uno-A-Erre and Gucci and seem to command a premium.
'uno (minus, really 'menos' in Spanish) uno' = 'one minus one'
uno means one (1). It can also mean the indefinite article "a" or "an".
Uno minuto mas -One minute more
One for all. All for one
The word "uno" in Spanish means "one" in English.
Numeral uno means number one in Spanish. It also means roman numeral one in Spanish which is "I". Edit: "numeral uno" actually means "numeral one". But you probably meant to write "número uno" which means "number one". It does not mean roman numeral one.
One and are (?)
What does this mean in jewelry?
If you mean the subtraction, that would be "dos menus uno". If you mean a hyphen, to separate parts of a code, that would be "dos guión uno".
viente uno
Treinta y uno translates from Spanish to mean thirty one.
Are you sure it's not UNO A ERRE? I've just been reseraching a pice of white gold jewellery with this mark on it and at first I took it to be UND A ERRE but on closer inspection it looks like an "O" rather than a "D" but a bit squared off. UNO A ERRE is a major Italian goldsmit and jeweller according to Wikipedia.