GT

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)

GTI

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.

Weblink: http://www.gtigmbh.de

GTIN

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)