I could used to do that.

source: 
LAGS
Entry: 
242
Example: 
I could used to do that.
Modal 1: 
could
Modal 2: 
used to
Gender: 
Female
Race/Ethnicity: 
White
Age: 
87
Level of Education: 
7th grade
Home Community, Town, or State: 
FL (Rock Hill)
Location Collected: 
FL (Rock Hill)
Year: 
1973
Relation to Addressee: 
female to fieldworker
Medium: 
Spoken
Sentence Structure: 
1.0
Status: 
Naturalistic