the thickness from 1.85 to 1.81 mm. Changes also effected the edge as the inscriptions of "NIPPON 500" were replaced with a helically reeded edge. The overall design was not changed but enhanced with anti-counterfeiting technology which include microprinting, and features viewed only at certain angles. This design later won the Mint Directors Conference award in 2002 as the "Most Innovative Coin Concept". It proved not enough to be a match against counterfeiters though, as they switched to using raw materials to get around the new security features. While in April 2019 the Ministry of Finance announced that the 500 yen coin would be redesigned, the new coins weren't released into circulation until November 2021. Bi-metallic yen The most recent 500 yen coins feature a bi-metallic three-layer structure that is also used for European coinage. One major difference are the edges of the coins, which use contour edging that utilize helical ridges with varied shaping. Two different colors are visible when looking at the coin giving it the name "bicolor clad". The center of the coin is made up of a silvery cupronickel, while the outer ring is golden nickel-brass. Aside from an increase in weight of 0.1g the coin's diameter remains the same as it has been since 1982. The overall design is the same except for a missing bamboo leaf under "500" which is replaced by the date (era). Enhanced features such as "JAPAN" and "500YEN" are also applied to the edge of the coin along with microprinting and angled features already present on the previous nickel brass issue. Redesigning the 500 yen coin was estimated to be 490 billion yen as it required the refurbishment of cash handling equipment. The COVID-19 pandemic pushed back schedules to circulate the coin which had initially been between April and September 2021. Other factors such as modifying vending machines & automated teller machines to accept the coins added to the delay. The new coins were finally released into circulation in early November 2021. This release did not invalidate old coins already in circulation as the cupronickel and Nickel-brass coins are still considered legal tender. While these coins are still valid, vending machines may no longer accept them due to their metallic signature. There continues to be a strong demand for 500 yen coins, and they are unlikely to be affected by electronic money. Designs Counterfeiting issues When the 500 yen coin