I was really lucky two find two Flavio Poli Sommerso pieces within one week
(Finally, investing in the Heiremans book pays off...)
A stunning (and huge at 32cm height) vase from 1958 in the green-amber-yellow colourway, model number 11994, one of two designs shown at the Expo 58 in Bruxelles.
This design is not found in the selective model list in the book, but there is a line drawing with the same measurements and cross section on page 359.
The colourway is "verde-topazio-giallo", introduced in 1957.
And a carboot find, a nice small ribbed vase ("Sommerso a coste") in green-amber, 17cm high, model number 12024, again from around 1958.