Here are two copies of A Shropshire Lad by A.E. Housman. Neither of these books fit into any known series. Both have the same dimensions (5.5 x 4.25) with identical interiors.
There are a couple of series that have a wreath on their covers. Those are the Worldly Wisdom Series (Series #195) and the Book of Love Series (Series #54). Neither of these series have A Shropshire Lad included in their book lists. This title is included in the Arcadia Series (Series #42). The books of the Arcadia Series are the same size as the books shown here. It is possible that variant covers of this series included the books shown here. This is purely speculation at this time. I believe both these books however are part of a series. But for now they belong to the unknown series section.