1965 carter afb carb
 

I have a carter afb carb without a metal tag, the only numbers on it is on the left front corner of the base and it reads c2 3721sb? I have found what the 3721 and sb mean but have not found anything on the c2. Someone told me it it meant month and year, but this series was not made in 62. Any help would be appreciated. Thanks Bear67