In 1984, Pilot marketed one such unusual—a pen with a squarish profile, a square prism in essence.
Pilot's Catalog from 1984. The Quatro trio—fountain pen, ball pen and mechanical pencil. All for JPY 11000. In this case, the nib was made of steel.
Pilot's 1989 Catalog. Quatro quartets —fountain pen, ball pen, mechanical pencil, roller pen— for JPY 27000. On this case, the fountain pen sports the gold nib (individual price, JPY 10000). On the right page, a view of the possible colors and finishes of the Quatro model. There were some aditional variations.
That was the Quatro (with just a single T), and it was available as fountain pen, roller, ball pen and mechanical pencil. They came in a number of colors and finishes –up to 16 according to some sources—, but some of them were only available as fountain pen. And to add confusion to the mix, there were some minor variations along the whole lineup—the brand name, Pilot, could be engraved on the front of the cap or on the cap; the model name was printed on the clip either on cursive script or on capital letters, or being completely absent.
Two nib materials were available: steel, for JPY 5000, and 14 K gold, JPY 10000. There was only one nib point—F. And the filling system was, needless to say, through proprietary cartridges and converters.
I do not have information on when this model was discontinued. My best guess, purely speculative, is in the early 1990s. However, the name Quatro was revived in 2007 through the model Quattro 89. But that will be the topic of another Chronicle.
My thanks to Mr. Furuya and Mr. Niikura.