Whilst unable to help directly, perhaps the following may be of use to you.
I am a retired shipmaster and liaise with other retired merchant seaman who, like me, once sailed with the Port Line Ltd. This is via a Yahoo Group Site “Vintage Port”(VP). I took the liberty of posting the essentials of your query on the VP site, thus identifying two such ex-colleagues who live in Malta.
One of these has offered his assistance when he shortly returns to Malta GC from UK. If you so wish, I can put you in direct contact.