(57) A double layered sheet, whereof the lower one (1) is made of common paper for food
products, the upper layer (2) is made of plastic film for food products, with the
two layers having nearly equal width, with two die cutting-folding, or simple folding,
longitudinal lines (3) and (4), able to subdivide the sheet into three bands (5),
(6) and (7) of such width as to enable the two lateral bands to be folded on the central
one and to superpose each other at least for a strip towards the free edges.
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