I use the same but altered to fit the dogs everyday collar..
She's mainly a bushing/ferreting dog and is off following her nose without the slip at night..
These catches are hard to find now,Johnsons fieldsports used to sell this type of slip lead, could do with someone usfull to start remaking them??would be interested in buying them, the bottom picture the catch has been adjusted, i also have a vintage version of this type of catch on a old knakered lead, used for running the dog with a collar, will put a pic up when i have time later