Much of Powell's work was done with assistants in a studio setting. So though only he gets credit here, it should be assumed that others had a hand in details and/or inking, including, possibly, Howard Nostrand, who did a lot of work with Powell.
from Man in Black (Harvey, 1957 series) #1 (September 1957)Splash page of The Man in Black introducing himself and the theme of the stories within.
from Man in Black (Harvey, 1957 series) #1 (September 1957)
from Green Hornet Fights Crime (Harvey, 1947 series) #34 (May-June 1947)A half-page strip, fills the bottom portion of the previous story's last page.
from Speed Comics (Harvey, 1941 series) #43 (May-June 1946)
from Green Hornet Fights Crime (Harvey, 1947 series) #38 (March 1948)
from Man in Black (Harvey, 1957 series) #1 (September 1957)