For example, this is a field-tested Desert Eagle below, and I would like to know what refer to its quality in the code. I know it have a quality id (), but this line is same (4) at all weapons, so this is why I'm asking this question.

[id] => 3293913951
[original_id] => 3293913951
[defindex] => 1
[level] => 1
[quality] => 4
[inventory] => 26
[quantity] => 1
[rarity] => 2
[attributes] => Array
(
[0] => Array
(
[defindex] => 6
[value] => 1119092736
[float_value] => 90
)
[1] => Array
(
[defindex] => 7
[value] => 1136440330
[float_value] => 377.40655517578
)
[2] => Array
(
[defindex] => 8
[value] => 1044836736
[float_value] => 0.19428062438965
)
[3] => Array
(
[defindex] => 147
[value] => models/weapons/stattrack.mdl
)
[4] => Array
(
[defindex] => 39
[value] => 0
[float_value] => 0.56000000238419
)
[5] => Array
(
[defindex] => 40
[value] => 0
[float_value] => 0.050000000745058
)
[6] => Array
(
[defindex] => 145
[value] => models/weapons/w_pist_deagle_mag.mdl
)
[7] => Array
(
[defindex] => 199
[value] => 35
[float_value] => 4.9045446251369E-44
)

Thank you for your answers!