Seitz, Werner G.: Pride the Copenhagen Coin Routine ©1970s (circa) The Supreme Magic Co., England Softcover, saddle-stitched, large format, 14 pages

Image from Magicref

Comments: Instruction manual for a coin through handkerchief effect that uses a clever gimmick. while I don't think the effect is sold anymore, you can likely make the gimmick using (perhaps, I haven't tried it) a bang ring or similar ring

Contents:

3 Introduction: the origins of the routine
5 The Copenhagen Coin Routine
5 The Effect
5 The Gimmick and Secret Preparation
5 Folding Instruction: for the handkerchief
8 The Routine: through page 13
14 Afterthoughts: additional ideas