Master keyed brass padlocks, each lock comes with 2 keys and you can buy a master key which will open all of them.
Each body size has a different master key.
If you prefer a combination padlock with a master key then click here > http://www.lockandkey.co.uk/products/Combination-Padlock-with-Master-key-and-code-reveal-Combi-reveal-107680.aspx