Phyllis Whitney 1903 to 2008

Still finding bits and pieces of artwork and managing to identify the title. This week it has been ‘Silverhill’ (1967)  by Phyllis Whitney. Although PAN published several titles by her I’ve only found one other example using the same style of cover ‘Snowfire’ (1973) She also wrote ‘Spindrift’ in 1975 which would seem to tie in with the others but is a completely different style.
What I would like to know is who painted the original cover? I’d suggest Michael Johnson but is it good enough for him?