#604 Dennis the Menace replaces Pansy Potter on the back cover. 1st appearance of The Bash Street Kids in a comic strip called When The Bell Tolls. #642 Fireworks (pictured). #649 Xmas (great full panel cover).
A VG Minus example of Beano #604 sold on eBay UK for £77.01 in August 2010 by phil-comics. Here is a great piece of research about the early evolution of The Bash Street Kids by Phil Shrimpton, the UK's top expert on The Beano:
"It is interesting to see how the characters developed in the very first issues. Many un-named "pupils" were present who failed to become part of the regular nine members that became the staple over the next 40 years; Danny, Toots, Fatty, Plug, Wilfred, Smiffy, Spotty, Erbert and Sidney.
Danny and Toots were both clearly visible in #602, Toots being named and Danny wearing his trade-mark black top with skull and cross-bones. A Fatty-like character is also seen in this issue.
Toots is again named in #603, with Danny leading the pack at the front.
The Porter was present in #604 and #606, but became the well-known Janitor from #607.
Danny is first named in #605, as is Fatty. Two characters, Tommy and Johnny are both named, but obviously didn't make it into the regular nine characters that we know today as The Bash Street Kids .
#606 sees the first appearance of Plug, although he is named Pug. His ghastly appearance clearly gives him away!
#608 is Danny's birthday. Plug is named Plug , and the strip contains other Beano characters such as Dennis the Menace, Pansy Potter, Biffo, Minnie, Lord Snooty and Little Plum.
#613 (Easter Issue) has the first named appearance of Smiffy, although he is covered in chocolate so difficult to see today's resemblance.
Plug is called Pug again in #614 and #616.
A character is in #615 looking very much like Wilfred, with his jumper pulled up over his chin, although he isn't named".