Hi Leni, I've checked through Mark Hill's book 'Mdina Glass & Isle of Wight Studio Glass' and although I can't find anything exactly the same as your bowl I would agree with your suggestion that the colour is early - 1971-72. There is a bowl in Mark's book on page 29 at the start of the section called 'Mdina Shapes 1968-1972' which, although a different shape to yours the colouring and stripes are very similar, this is described as 'A Mdina Glass bowl with an inverted lip and flat polished base signed 'Mdina', designed by Michael Harris c1971'.