It looks like a Cay Caulker to me. Kind of hard to tell just by pictures though.
Technically, a Cay Caulker and a Belize boa are not the same. They are both B.c. imperator but from different insular localities. Here is some info that might help you...
http://www.boa-constrictors.com/en/b...ze_cay_caulker
http://www.boa-constrictors.com/en/b...ze_cay_caulker
I would not think your snake is a Belize - they are pretty rare in herpetoculture. Cay Caulkers, while not too common, are not that rare.