A quick visual survey of known sets of Rosen's Hallowe'en Trix or Treats lollipop-holder cards (with variations of style shown here dating from the 1930's to the 1950's).
The first seven-card set (at right, below) were produced in beautiful full color during the 1930's. A similar set (shown left, below) followed with faithfully redrawn art with somewhat cleaner lines and a more mono-chromatic color scheme heavily reliant on traditional orange and black. The left set dates during the 1940's --- (there is handwriting on the back of one with a name and the year of 1946).
1940s (left) - 1930s (right)
The art and size of Rosen's cards were overhauled some time during the 1940's. And while curiously the owl is a continued presence, there are instead four different accompanying cards featuring more fantastic Hallowe'en creatures such as ghosts, dancing skeletons, and witches (one witch as a slight variation of previous imagery). While minimal in comparison to previous art, the colors and imagery retain a magically creepy quality. (I'm "a sucker" for blue in Halloween color schemes).
One final set is said to date in the 1950's. The owl again returns, as do images from the original sets. Fairly rough imitations of the originals with colors schemes of wan oranges and browns, I might venture to say this latter set may be for completion-collectors only.