RPG-18 is a
straight copy of the M72 Law. The RPG-22 is a further development of the RPG-18. The RPG-26 is a further development of the RPG-22 and also comes in RShG-2 variant, armed with a thermobaric warhead. RPG-27 was developed from RPG-26, with a tandem-charge HEAT warhead. This also comes a RShG-1 with a thermobaric warhead.
See:
http://www.forecastinternational.com/samples/F654_CompleteSample.pdf
also:
Modern Firearms - RPG-18 disposable grenade launcher / rocket-propelled grenade
M72 is so widely available (hundreds of thousends of rounds!) and used by so many parties, its mere presence does not provide enough to go on (you'ld need specific production batch info and export info). For
example, in 1986, it was clandestinely shipped to Chile to arm an outlawed branch of the communist party, an operation overseen by
Cuban intelligence, aided by
East German and
Russian intelligence services. It is also used by the military of Mexico and - subsequently - by a Mexican drugs gangs (Los Zetas), which consists of army deserters ....