GT refers to a coated secondary fibre board.

Front top layer = hf white or light hh white
Inlay = grey
Back cover layer = light

hf white: wood-free white layer of bleached pulp with a maximum of 5% mechanical pulp

light = light layer of mechanical wood pulp or of a mixture of unbleached pulp and mechanical wood pulp

grey = layer of recycled pulp (reused cellulose and groundwood fibres)


The GTI GmbH is beside Just Normlicht a renowned manufacturer of standard light tubes and standardized light consoles and colour cabins. GTI offers numerous systems for colour assessment, but is- other than Just – opposed the use of LED, and therefore offers only special neon-based solutions. LEDs in the standard light industry are according to  GTI economically and qualitatively no real alternative to the renown and tested tubes.




The Global Trade Identification Number is synonymous with 8- and 13-digit bar code.

The EAN or better: GTIN numbers contain the issuing country and a reference to the manufacturer as well as a serial product number and a check digit. The numbers are assigned worldwide by GS1.

The Proof GmbH is a member of GS1.

An article with tips for creating GTIN numbers for graphic designers can be found here. (German)


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