Excentro: Guilloches made on a Mac

"Excentro is a simple but advanced tool that can create guilloche designs like backgrounds, borders or rosettes.

The guilloches are vintage design elements that were frequently used for anti-counterfeiting security purposes on banknotes, passports, checks and certificates during the past two hundred years. As the times changed and digital copy and printing technologies perfected, guilloches no longer presented sufficient security measures that could prevent forging and counterfeiting of valuable papers. Today the main part of security technology lies in the special paper or tricky inks the designs are printed upon or with." (Thanks Chris Glass!)