The card or a piece of paper with your information in the seat tube is time proven. Every case I have heard of ended in the rightful owner getting their bicycle back and the thief being successfully prosecuted when charges were pressed. Two were here in Escambia County, FL back in the late 70's. Seen several instances recently out of our area that had this used to reclaim a bicycle from some dink that was a thief.

As said by FBinNY, make sure you laminate, or place the paper in a plastic baggie, to keep in dry and legible. Disproving the low life, just have the above methods or recording the serial numbers photographically with your home and/or garage viewable in each picture with time and date stamp. I am a notary for Florida, any cyclist wanting this notarized just needs to ask, and its done, gratis, and recorded by me in my ledger.

Bill