BOP - a cartoon character's punch? BOP - early modern jazz??
No, in fact it's Boy's Own Paper which after its founding in 1879 quickly became known as B.O.P. and has entered into English with the phrase "It's just like a story out of Boy's Own Paper" when incredible tales of heroism and derring-do are being discussed.
Left: The attractive cover of Volume 10 (1887-8)
The B.O.P was issued weekly by the Religious Tract Society to combat the "penny dreadfuls" of the day and was to be "pure and entertaining" reading with a steady stream of recommendations for curing impure thoughts and, much worse for boys, impure actions!