Top break revolvers (Iver Johnson, Harrington & Richardson, etc) were latched closed by a loop or stirrup that hooked over the locking posts. There were designed for low pressure, black powder cartridges. As higher pressure smokeless rounds appeared, the top breaks faded away in favor of the solid frame revolver.
Pistols such as the Contender use a totally different locking system. It is not affected by an unsupported frame stretching. Locks up with a lug on the bottom of the barrel, like a top break rifle. Notice that you will find the old top breaks in .32 S&W, .38 S&W, but not .38 Special, .357 magnum, etc.