The class was originally planned to serve as Convoy Rescue Transports (designated as APR), however the idea was abandoned before construction started.

[3] As a medical ship, she was built with an onboard surgery, pharmacy, 65 hospital beds and equipped with x-ray devices with accommodations for 57 patients.

[3] A common criticism of the design was the lack of long range surface detection equipment, which forced the crew to manually watch for aircraft.

The problem was also compounded by the lack of a short range radio, meaning the ship was not able to get any warnings of incoming aircraft from nearby units.

PCER-851 and sister ship PCER-852 began operating in coordination with each other, sharing men and supplies while anchoring together to combine anti-air capabilities.

PCER-851 suffered a friendly waterline shell hit[6] en route to Mindoro before shooting down a Japanese aircraft, and later on aided in firefighting and survivor rescue.

On February 15 she made for the Volcano Islands to screen the approach, before she focused on beach patrols after arriving at Iwo Jima.

[6] At 0610 on 1 April about ten miles off Hagushi Beach, a Zeke kamikaze took the crew by surprise before diving on the ship and barley overshooting, crashing astern.

[6] To further bolster anti-air capabilities, the ship's gunnery officer was traded medical whiskey for single and twin 50 caliber machine guns with aviation personnel.

[6] She would continue patrolling duties until the 6th, where she rescued survivors and bodies from kamikaze damaged ships, including USS LCS-82, Maryland, Laffey, Morrison and Ingraham.

[6] PCER-851 left the island chain on 28 June, where she docked at Saipan on 4 July and escorted USS Rockwall to Pearl Harbor, arriving on the 19th.

[10] On 15 February 1956 the ship was renamed Rockville after small towns in Connecticut and Maryland, followed by being fitted with an electronics laboratory and workshop.

[4] In 1968 the United States Congress passed the Revenue and Expenditure Control Act of 1968, which reduced the US Navy's budget by US$913 million.

[4] On 5 June 1969, Rockville was transferred to the Colombian Navy as a survey ship under the name ARC San Andres (BO 151).