i looked into my copy of The Panzerkampfwagen IV Book 2 from Schiffer by Spielberger, Doyle and Jenz.
On pages 143 and 144 you see the interior of the turret how the Sehklappe (vision ports) are mounted with 3 bolts on the left and four on the right, 2 top, 2 bottom..
But in Spielberger's earlier book, Panzer IV and its variants, on page 37 there is an overhead view of a Ausf. E turret with 3 bolts over both vision port covers.