Ruben Beck was Marine who served during the latter half of the 19th century. According to the biography posted he did not serve in the Zulu War. He is definitely not the R. Beck on the "Euphrates" roll. R. Beck was a navy man rated as a Stoker.
"From February 1879 to June 1884 he was a sergeant, based at Chatham."
"From February 1881 to March 1884 he served with the Flora, in South Africa."
"In February 1884 he was discharged from his ship, and given mail steamer passage to England. He had apparently been involved in the war with the Zulus - he returned to England with a Zulu assagai and shield."
The closest he could have been to the Zulu war is if he was a member of the Marine Battalion that was sent out on HMS Jumna, and then held at Simon's Bay until Garnet Wolesley decided that the war was coming to a close and ordered them home. As a consequence he was not entitled to the medal.
Petty Officer Tom