Depicts the portrait of Donát Bánki. Above the portrait, the inscription "BÁNKI DONÁT" is visible. To the right, in horizontal rows beneath each other, the birth and death years "1859-1922," the inscriptions "THE BÁNKI-TYPE", "WATER TURBINE", and "INVENTOR" can be read. In the bottom right corner, the engraver's privy mark is located.

Depicts the crossflow turbine. Positioned horizontally below the turbine depiction are the words "HUNGARIAN" and "REPUBLIC," with the denomination and the word "FORINT" appearing above them. Adjacent to the central design, aligned with the left edge, is the year of minting "2009," while the mint mark "BP." is situated parallel to the right edge.

The cross-flow turbine, also known as the Bánki-Michell turbine or Ossberger turbine, emerged from collaboration among Australian Anthony Michell, Hungarian Donát Bánki, and German Fritz Ossberger. Michell patented his turbine design in 1903, manufactured by Weymouth for many years, while Ossberger secured patents in 1933 and established his eponymous company as a leading manufacturer. Unlike conventional water turbines, the cross-flow turbine directs water across its blades, enhancing efficiency and self-cleaning. Ideal for low-head, high-flow locations, it features a low-speed design and often incorporates two nozzles to prevent flow interference. These turbines are commonly built with dual capacities, sharing a shaft but varying in wheel length to accommodate different volumes under the same pressure. Flexible operation and low maintenance costs characterize their construction, making them a practical choice for various hydroelectric applications.