I had one of those buckle derringers too. I think they were made by Mattel and used "Greenie Sick-em Caps." I also had a "Fanner 50" that looked like a Colt SAA, it used the self-adhesive caps too. There was a local (Louisville, KY) TV show (WHAS Channel 11) back in the late 50's/early 60's called T-Bar-V, it was a cowboy/kid's birthday show and between cartoons kids would go in front of the camera, where the show host Western singer Randy Atcher and his sidekick Cactus Tom Brooks would let you wave and say hi to your parents and relatives. After that Randy would count to 3 and you could fast-draw your six-shooter...of course I had my Fanner 50 and derringer and was in my Hop-Along Cassidy outfit! Those were the days...