Daryl has posted pictures of a a rifle I made. The original rifle(s) that I was using for reference had keys like those of the OP's pictured rifle. But I remove my barrel every time I clean it, so I made slides that engage the lugs in the barrel but do not perforate the escutcheons on the other side of the stock. Instead, I simply drilled a 1/16" hole in the escutcheon plate to insert a pin punch to push out the slide. I've never used the hook and pin method bama describes, but it sounds intriguing.
On my rifle, the heads of the slides are pure silver silver soldered to brass slides. And they are captured slides, so they cannot be completely withdrawn, or lost.