The two mystery ships are readily recognisable as (on the left) one of the five Monte Class built in 1924-31 for the Hamburg-South America Line, and (on the right) the second Laurentic completed in 1927 for the White Star Line.
Laurentic (18,724gt) was built by Harland & Wolff, Belfast in 1927. She was propelled by triple-screw combination machinery of 15,000ihp (i.e. triple-expansion main engines on the wing shafts, plus a low-pressure turbine on the centre shaft), which produced a service speed of 16 knots.
Laurentic served on the Canadian serviceuntil being sent on cruises from 1932. Following the Cunard-White Star merger in 1934, she was used only for cruising, and was laid up in 1935. She made only one trooping voyage, to Palestine in 1936, and was requisitioned as an armed merchant cruiser in 1939. On 3 November 1940 she was torpedoed and sunk. Laurentic was unsual in that she was the last major North Atlantic liner with coal-fired reciprocating machinery.
The other ship was one of five almost identical sisters, all named after mountains in Tierra del Fuego. The class comprised Monte Sarmiento (1924), Monte Olivia (1925), Monte Cervantes (1928), Monte Pascoal (1931) and Monte Rosa (1931). All measured 524ft and had twin-screw MAN diesels, with a speed of 14 knots. But which of the five is our mystery?
This can quite be narrowed down to the last two, Monte Pascoal and Monte Rosa, since only they had their promenade deck extended forward beyond the bridge and I would suggest that the subject ship is Monte Rosa.
Robert H. LangloisVale, Guernsey