He had the PMG qualification as described here, from the Wireless college Colwyn Bay website
"RADIO OFFICERS in the BRITISH MERCHANT NAVY or at BRITISH COAST STATIONS are required to hold a certificate of competence issued by H.M. Postmaster-General. P.M.G. Certificates are issued in three grades - SPECIAL CLASS, SECOND CLASS and FIRST CLASS; the minimum training periods (for students following a standard course) being 2 1/2 terms, 3 1/2 terms and 4 1/2 terms respectively.
The SPECIAL CERTIFICATE entitles the holder to operate apparatus in small ships, such as fishing vessels
and private yachts which are not by law compulsorily fitted with radio. Because of its limited usefulness, training for the Special Certificate alone is not recommended.
The SECOND CLASS CERTIFICATE entitles the holder to serve as a junior Radio Officer in any British ship and as the Radio Officer-in-charge in some British ships.
The FIRST CLASS CERTIFICATE entitles the holder to be the Radio Officer-in-charge of the entire Radio installation and the Chief of the entire Radio staff in any British ship. "
https://sites.google.com/site/wirelesscollege/college-prospectusI think this is the ship he served on
https://uboat.net/allies/merchants/crews/ship1295.htmlI do not know what the numbers on the 1939 snip refer to.
There are crew lists for this ship, if it is the correct one, at the national archives
https://discovery.nationalarchives.gov.uk/results/r?name=Search&_cr1=BT%20381/552&_aq=171309It may also be worth doing a search of his name here
https://www.crewlist.org.uk/people/crew