Take a look at this larger cropped detail from the original art. The line work in the printed comic, reduced from the original, looks very tight and precise; but Yandoc's art shows just how freely and energetically the ink was applied to the page.
Rubeny was one of many Filipino comic book artists that DC began using in the 1970's. From what I recall reading, DC was having a difficult time finding enough good comic book artist to fill their needs. Artist Tony DeZuniga was doing some work for them and was responsible for getting many other Filipino artists published in the US markets.
art @ DC Comics