Now I will try with this scan

Just ignore the r2c4 Mariano Moreno (scanning take it's time so scan several stamps at once)
here it is a back scan

r1c1 is MI4 => click here for my analisys
r1c2 is MI1 => click here for my analisys
r1c3 is RR1 => click here for my analisys
r1c4 is MI3 => click here for my analisys
r2c1 is MI3 => click here for my analisys
r2c2 is MI3 => click here for my analisys
r2c3 is MI3 => click here for my analisys
So far all of them with symmetrical lines.
Thanks
Sergio