As far as I could tell, the Brazil 1970 Census microdata is missing the municipality (source) variable.
For the other years, the equivalent variables are: BR1960A_MUNICIP, GEO2_BR1980 GEO2_BR1991, GEO2_BR2000, GEO2_BR2010 (the standardized var is GEO2_BR and is for the 1980-2010 period)
I believe the municipality codes are in variable BR1970A_STRATA because the municipality is the stratification unit of the Brazilian Census. Also, this variable has 6 digits, which is the number of digits of Brazilian municipality codes (without the verification digit)
OBS: this may be related to my other question on birth municipalities