Kilogram mass standard, prototype number 20
The US national prototype kilogram, number 20, a metal cylinder with a number engraved on its side, photographed by the National Institute of Standards and Technology.
Open the original (4,416 × 5,711 px) (opens in a new tab)
- By
- National Institute of Standards and Technology
- Licence
- Public domain (opens in a new tab): free for any use, including commercial
- Source
- Wikimedia Commons (opens in a new tab)
- Tags
- kilogram, weight, mass standard, metrology
Credit (appreciated, not required)
Photo: National Institute of Standards and Technology via Pixy (https://pixy.org/4218630/)
