Likely from mid-1980’s commercial item (catalog here: http://soldiersystems.net/2017/02/21/lowe-vector-catalog/).
Design eventually became standard issue CFP-90 although this earlier one had a better build quality (source: http://oefoif.forumotion.net/t8059-lowe-vector-i-woodland-camo-rucksack).
Detachable waist belt and integrated rapelling system:
Back pad is removable and attached to frame with velcro:
Fabric is like a green dominant ERDL (smaller print than real M81 woodland) and is similar to ALICE pack (400 or 420 denier packcloth) material, like SADF Niemoller Vest.
No date codes on any plastic buckles:
Buckle could be from 1984 – 1985 (source: http://survival-knife-184.com/sheath/sheath.html).
Russian Language forum thread about this model of rucksack: http://www.gearguide.ru/phpbb/viewtopic.php?f=18&t=383