Since the serials are present,
DL30? DL302, was a Master mark II Mercury XX engine
W8513 and W8518 were Master mark III Wasp Junior engine.
The R-1535 was an interesting choice, 602 Master III built January 1941 to October 1942, versus 1,291 R-1535 produced January 1940 to end of production in February 1941, with a whole 5 R-1535 imported into the UK after 1 July 1941.
W8513 on strength 11 June 1941, off 15 Apr1l 1944
W8518 on strength same date, no off date.
DL302 on strength 19 May 1942, off 27 March 1950.