The British medal is the Sea Gallantry Medal (Foreign Services), which was awarded to Van Iersel for his actions while serving on the Danish merchant vessel s.s. Oluf Maersk:
On 2 February 1917, the schooner Little Secret, of Fowey, was in a sinking condition in the North Atlantic Ocean. In response to signals of distress the Oluf Maersk, approached the vessel and launched her lifeboat under the command of Mr. Godtfredsen and manned by the seamen named. After considerable difficulty the Little Secret was reached and her crew of five hands were takenon board the Oluf Maersk and convoyed to New York. Very considerable risk was incurred in rendering the services, on account of the heavy seas which prevailed at the time.
The seamen mentioned:
Mads GODTFREDSEN, Second Mate
Christian Bernhard NIELSEN, seaman
Niels Peter SIMONSEN, seaman
Luderus Matheus van Jersel, seaman
Source: The Sea Gallantry Medal by R.J. Scarlett (OMRS, 2010).
As can seen, the name of Van Iersel is misspelled in this book. I came across his decoration in a Dutch newspaper article from 25 June, 1925, which stated that Van Iersel, before joining the U.S. Army sailed in the merchant navy. During that period he saved the life of five persons and got awarded both British and U.S. Lifesaving Medals. So appearantly one of the unknown medals yet to be determined is a U.S. Lifesaving medal.
The article also mentioned that Van Iersel received, beside these medals and the Congressional Medal of Honor 14 medals and 8 honorable mentions, amongst which: the Distinguished Service Cross, the French Military Medal, 2 Croix-de-Guerres with palmes and stars.