House flag of ABC Container Lines
Antwerp Bulk Carriers, better known as ABC Container Lines, was founded in 1978; five round-the-world container bulk ships (Europe-Australia-USA-Far East) were operated before the firm had to close down because of financial difficulties. At one time TNT owned part of the company; ships sailed under the Luxembourg flag.
According to Brown's Flags and Funnels of Shipping Companies of the World (1995), the house flag of Antwerp Bulk Carriers is orange with a white diamond (slightly rounded) charged with the city skyline in blue and the black letters ABC.
The tower shown on the left is the Boerentoren (Farmers' Tower), an interbellum skyscraper; in the middle is shown the Notre-Dame Cathedral; the building in the left may be the Steen, the ducal castle built near the river Scheldt.
A table flag resembling this one, identified as ABC Container Line, Antwerp, appeared on German eBay in February 2007. The flag is bright red and bears an elongated diamond (with the longer vertical) showing two towers in blue, the Boerentoren on the left and the Cathedral's completed tower and unfinished one on the right. Black initials in a curved line are placed on the blue silhouette. The dimensions of the flag are given as ca. 14 cm x 22 cm.
A photo showing an orange funnel bearing the same logo as the table flag includes in the caption "the now defunct ABC Container Line of Belgium while at Port Chalmers, 15 January 1991". Other photos mention the, also defunct, Cockerill Yards at Hoboken as the wharf where a number of ABC ships were built.
Could it be that Loughran manhandled the diamond and that the red shade on the eBay offer is indeed orange? If so, judging by the funnel, the real flag would have been like the eBay item, with an orange field.