Lomonosov (Russia)

My Lomonosov turned around chipmunk was sculpted by I Y Vorobyev. Does anyone know how I can date him as he's completely unmarked? He seems to have longer ears then the current
model


PS Is Russia covered by Europe or do we need a new section?

The fact he is unmarked is not suprising as the inks used are soluable A good wash and they have all gone
A picture might help but identification can be a mine field as the russians wernt that good at documentation plus any is usually in russian
Here are two pieces from the USSR which means before 1991 Russia after
A ruse on the trade of these at there hieght of fashion?? was the removal of the R and the a in Russia (ussr pieces fetched three times the russian ones (playing field has now leveled and there is not that much differance) ) then claim the R in USSR had just lost its squiggley bit