@codewiz You know, stuff like that is the perfect nerd-sniping instrument for me (it's fun, so nevermind 🙂 )
The company is mentioned in an EU anti-dumping duty proposal for weighing scales in 1993: https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:51993PC0087&from=GA refers to "Santo Stefano S.p.a., Cassano Magnago, Italy"
https://www.gazzettaufficiale.it/atto/parte_seconda/caricaDettaglioAtto/originario?atto.dataPubblicazioneGazzetta=1991-04-08&atto.codiceRedazionale=M-4102 shows a company with its offices in Cassano Magnago but registered in Milano.
They moved their main office to Binasco in 1991: https://www.gazzettaufficiale.it/atto/parte_seconda/caricaDettaglioAtto/originario?atto.dataPubblicazioneGazzetta=1991-08-07&atto.codiceRedazionale=M-7867 (move), https://www.gazzettaufficiale.it/atto/parte_seconda/caricaDettaglioAtto/originario?atto.dataPubblicazioneGazzetta=1994-04-14&atto.codiceRedazionale=M-3783 (new official residence)
The chairman of the board merged it with two other companies he controlled in 1994: https://www.gazzettaufficiale.it/eli/id/1994/11/14/M-8799/p2
In 1995 it was renamed to "Dataprocess Industria" (https://www.gazzettaufficiale.it/atto/parte_seconda/caricaDettaglioAtto/originario?atto.dataPubblicazioneGazzetta=1995-02-27&atto.codiceRedazionale=M-802), which still exists under that name.
https://www.catawiki.com/en/l/32790233-santo-stefano-varese-balance-or-scale-1-glass-iron-cast-wrought claims that the scale was produced in the 70s/80s.