Here is Pik-20 measurement by Dick Johnson from past.

The some factory,
the some technical control,
the some workers, the some design,
the some...
...and differences

Gliding production is not inwardness serial production if with serial numbers "operate".

http://www.appledor.net/tsillas/soaring/pikt7/pikt7.htm

Prototype was excellent,
s/n 8 was abortive,
s/n 145 was great
later model excellent...

VHZ