Huish has issued a recall on some Oceanic and Hollis regulators. Please see this page to find out if the one you have has been recalled. The serial number is on the first stage of the regulator, but the UPC and part numbers are only available on the packaging.
According to Huish, the recall is due to some regulators restricting airflow for tanks below 500 psi. This can be remedied with a repair and affects about 4,500 units.