Here you go.
SS RUFUS C. DAWES (note full name) was built in 110 days by St. John's River Shipbuilding, Jacksonville, FL, between May and September 1943. She was scrapped in Tacoma, WA, in 1968. See http://shipbuildinghistory.com/history/shipyards/4emergencylarge/wwtwo/stjohnsriver.htm and scroll to hull number 12. Also see http://www.mariners-l.co.uk/LibShipsR.html and scroll to the name of the ship. The ship was named after Rufus C. Dawes (1867-1940), president of the Chicago World's Fair in 1933, and president of the Museum of Science and Industry in Chicago 1934-1940. (I know, big deal.)
SS JOHN SERGEANT (the correct spelling) was built in 61 days between July and September 1942 by the Bethlehem Fairfield Shipyard, Baltimore, MD. Interestingly she was under construction in the same shipyard at the same time as was SS JOHN W. BROWN, one of only two surviving, operational Liberty ships and aboard which I serve as a volunteer crewman. JOHN SERGEANT was completed two weeks before JOHN W. BROWN. JOHN SERGEANT survived the war and in 1956 was converted to a experimental gas turbine-powered configuration. (All Liberty ships originally had triple expansion steam engines fueled by oil.) See https://docs.google.com/file/d/0B2KS6sfqM0fOSU5TR0E1dFBTTmlDeVp0a1AzZkFxdw/edit?pli=1 for information about this experiment. She was scrapped in Portsmouth, VA, in 1972. See http://shipbuildinghistory.com/history/shipyards/4emergencylarge/wwtwo/bethfairfield.htm and scroll to hull number 2050 (JOHN W. BROWN is hull number 2062). Also see http://www.mariners-l.co.uk/LibShipsJo.html#JohnH and scroll to the name of the ship. The ship was named after John Sergeant (1799-1852), a member of the U.S. House of Representatives from Pennsylvania 1815-1823 and 1837-1841, and an unsuccessful candidate for Vice President in 1832.
The Armed Guard crew of SS JOHN SERGEANT received battle stars (for participation in battles with the enemy) in November 1942 (landings in Algeria and Morocco), July 1943 (invasion of Sicily), and August-September 1944 (invasion of southern France). See http://usmm.org/battlestar.html and http://usmm.org/battle-g-m.html.
See http://baltimoresun.imagefortress.com/search/asset_details/1505035?adv[query]=%40folder_description+%22SS+JOHN+SERGEANT+%28SHIP%29%22&page=1&results_index=0 for a photograph of the gas turbine engine being lowered into JOHN SERGEANT at an unidentified shipyard in 1956.
Of greater interest to you, of course, is the whereabouts of each ship during the war, and particularly while your uncle served in each. For this, go to ConvoyWeb (http://convoyweb.org.uk/hague/index.html), an excellent website that records the convoys in which ships sailed, ports of origin and destination, applicable dates, and sometimes a small amount of additional detail about individual ships although nothing about the crew. At ConvoyWeb do a "Ship Search" using the (correct) name of each ship. Presumably you know from his service record when your uncle sailed in each ship so you should be able to match up those dates with the results of your Ship Searches to determine where he was at various times. I did searches for each ship and found that both crossed the Atlantic several times into the Mediterranean and/or to Britain. You can also search for each ship at a different website, Warsailors.com (http://warsailors.com/search.html), which is similar to ConvoyWeb. ConvoyWeb is more comprehensive but Warsailors sometimes has more detail on individual convoys and individual ships. I found information on both ships at Warsailors.
And there's always the good old Google search. Use the full and correct name of the ship and add the "SS" (meaning steamship) designation so as to avoid searching for the men of the same name. You never know what else you might find.
If you want to obtain your own photographs of the two ships, see http://www.usmm.org/photosource.html for sources of photographs of World War II-era merchant ships. Your best bet is Mr. Hultgren, since his collection focuses on Liberty ships; both of the above ships were Liberty ships. I know enough about his collection to know that he apparently has images of both ships. I understand he charges $10 for an 8x10 print. Mr. Hultgren is quite elderly but at last report he was still actively managing his collection.
Ron Carlson, Webmaster
Armed Guard / Merchant Marine website