I used to could work all day.

source: 
LAGS
Entry: 
674
Example: 
I used to could work all day.
Modal 1: 
used to
Modal 2: 
could
Gender: 
Male
Race/Ethnicity: 
White
Age: 
82
Level of Education: 
7th grade
Home Community, Town, or State: 
TN (Laurel Bloomery)
Location Collected: 
TN (Laurel Bloomery)
Year: 
1971
Relation to Addressee: 
subject to fieldworker
Medium: 
Spoken
Sentence Structure: 
1.0
Status: 
Naturalistic