Thank you for submitting your item for appraisal. This appears to be, just as you stated a fragment of mayan terracotta figurine. The patina appears to be authentic, the provenance and certificate is the indispensable necessity to sell such things today. The estimate is based on similar items offered or sold at auction recently. The newly introduced regulations on cultural heritage protection laws had an impact on the antiquities market. Currently demand for smaller pieces is rather low.