Conversation so far:
when did the us start putting strips in money
The first new-age anti-counterfeiting measures were introduced under Series 1990 with microscopic printing around Franklin's portrait and a metallic security strip on the left side of the bill.
what other anti-counterfeiting measures are there for currency besides microscopic printing and metallic security strips
National engraving bureaus include anti-counterfeiting systems for currency, such as holograms, multi-colored bills, embedded devices such as strips, raised printing, microprinting, watermarks and color shifting inks, and more.
what anti-counterfeiting measures does the twenty dollar bill have
The United States twenty-dollar bill's security features include security fibers, watermark, security thread, color shifting ink, micro printing, raised printing, and the EURion constellation.
what does the eurion constellation do in a twenty dollar bill
The EURion Constellation is intended to prevent color copiers from reproducing images of contemporary currency.

Question: when was the constellation invented
Self-contained rewrite: when was the eurion constellation invented