Cari amministratori / editors, Ah bene, anche Savona e Genova ci tengono compagnia coi numeri rossi allora!
Sì, sì, anche "9a rosso" ci sembra un modo chiarissimo di scrivere il numero civico dell'ufficio nel quale abbiamo entrambi la sede legale delle nostre rispettive Partite Iva  :-) :  )  ; anzi, forse anche più chiaro!
Quindi per favore sì, scrivetecelo così, sulla cartina topografica: 
"9a rosso".
I ns. più cordiali saluti, 
Alberto Zaccagnini e Fumiko Zaccagnini
Via Faentna 9a rosso, CAP 50133, Firenze.
P.S.
In the very same place, Via Faentina 9a rosso, 50133 Florence, Italy, : "AZ Language Services [di Alberto Zaccagnini]" (a one-person business registered with the Italian VAT Authority) offers: 
1)  tailor-made  individual and small group TOURS  in Florence; and in what used to be called the Province of Florence, and the Chianti area; as well as in Tuscany and in Italy in general.

*Alberto is a licensed and authorized Italian Tourist Guide, authorized for English, French, and Japanese*, and also speaks  some German. 

2) TRANSLATING and INTERPRETING between English-French-Italian- and, in collaboration with his Japanese wife, i.e. native speaker  Mrs Fumiko Zaccagnini,
raised and educated in Japan , also TRANSLATIONS into and from JAPANESE.

3) Alberto teaches "Italian as a Second Language", one-to-one and to very small groups.

In the very same place, i.e. in Via Faentina 9a rosso, 50133 Florence, Italy, : "AZ Japan Services [di Fumiko Zaccagnini]" (a one-person business registered with the Italian VAT Authority) offers: a) lessons of Japanese for people from any country, and b) TRANSLATION & interpreting  between Japanese-English-French and Italian.

So, we would like to be categorized as 1) TOURIST GUIDE+ 
2) TRANSLATORS+ 
3) INTERPRETERS+ 
4) Italian & Japanese LANGUAGE TEACHERS; 
= as far as possible.

Thank you for your kind attention and time.

Written by: Alberto Zaccagnini and Fumiko Zaccagnini on 9th of September 2023.