gbalke

I believe the hump is just a design aspect of the bike.

This is from Oldroads.com:

These were top of the line Raleigh bicycles finished to the full standard of the Sports. That is, Raleigh patent wheels ("Westrick"), brazed fender stays instead of the cheaper bent wire (fewer rattles), and brazons where the lower eschelon models used clamps. The Colt was intended for juveniles and came with 5.5 inch cranks (difficult to find). The boy's model had a distinctive curved top tube.