'Other' Constructional and Allied Systems Info & Downloads
Konstruktor(15) was a metric system similar to Eitech Construction. It has a few unique parts. It was made in Russia by OJSC Michurinsky Plant "Progress" (ОАО Мичуринский завод «Прогресс») from at least 1981 to at least the early 1990s.
Manufacturer / Distributor
OJSC Michurinsky Plant "Progress", Russia (ОАО Мичуринский завод «Прогресс»)
Info from the Metal Constructional Systems Database for KONSTRUKTOR 
Hole pitch <12.7mm
known in early 1980s (some significant doubt)
(see comment *1)
Bolts: round (slotted)
Small set including 5 holes diameter Disc with rectangular hole pattern. Lid has a dumpy 'boy' waving a Spanner. *1 Axles with screwed ends.
Below there are manuals/leafets which can be downloaded by clicking on the appropriate image.
Photos of the Konstruktor(15) tank set of 1980. The set was made from copper plated steel.