From this archive site apparently about the Cresuot company, they list, amongst other equipment:

- USINE DE SAINT-CHÉLY-D’APCHER (Lozère) : aciérie (fours à arc, four
pour fluoalliages), laminoirs (train à largets, cages duos pour tôles, quarto réversible pour tôles magnétiques, équipements de parachèvement), centrale hydroélectrique : 1965-1966

It sounds as if there may be some relation here cages duo / quarto, I'll try and dig a bit deeper.

http://www.afbourdon.com/centrearchivind/etatsommaire/etatso...

Further down:

Creusot-Loire :
- CRÉATION DE CREUSOT-LOIRE :
- ACIÉRIES BREUIL : fours électriques, équipements de coulée, affinage en poche chauffante, équipements de levage et de manutention : 1977
- LAMINOIRS : tôlerie forte du Creusot : trains duo et quarto, fours, cellules de réchauffage des lingots, équipements de parachèvement (1977)

and again:

Equipement sidérurgique :
RPR-Galati : laminoir Quarto (1963)

So it looks like it might be some kind of laminoir (perhaps with 4 rollers instead of 2?), and from the capital letter, I even wonder if it isn't a brand name?



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Note added at 5 hrs 12 mins (2005-04-11 15:54:55 GMT)
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Page 10 of this document gives various information and a photo of a cold-reversing mill (laminoir quarto réversible) --- though I would be a little suspicious of that translation myself...

http://www.edpsciences.org/articles/metal/pdf/2000/11/p1371....

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Note added at 5 hrs 13 mins (2005-04-11 15:56:06 GMT)
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And finally, GDT gives the translation of \'laminoir quarto\' as \'four-high mill\', which seems to make peferct sense to me!