I've occasionally kept looking for more info on R. Cooper. My landscape has a signature exactly like the one on "the Sphinx" you mentioned. I', less certain about "pitcher plant" since I can't find a signature.
Today I found this info (on this web page:
http://www.bigskyfine...ooper-r/on-the-nile):
Reginald Cooper
fl.1929-1939
British
On the Nile
Signed & bas droite
Watercolour
38cm x 19cm
Reginald Cooper was a painter and illustrator, chiefly in watercolour, of rural scenes and landscapes. He was a prolific artist between about 1929 and 1939 and many of his works have been reproduced as prints and postcards. His work is attractive and becoming very collectable. This is a stunning watercolour entitled On the Nile.
This is the same signature on my watercolor.