Currency symbols

You can find any keys by showing the keyboard viewer.

Go to System Preferences->Keyboard->Input Sources and check “Show Input Source in Menu Bar”.

A little menu with a flag corresponding to the active keyboard layout will appear in the menu bar. In this menu you will find two very useful entries: “Show Keyboard Viewer” and “Show Character Viewer”.

You're welcome. The Keyboard Viewer is handy to be able to find various keys. Open System Preferences > Keyboard > Keyboard and mark "Show keyboard and emoji viewers in menu bar". Then you can just open the Keyboard Viewer from the icon, and press various modifiers such as shift, option, option + shift.

On the US keyboard £ is "Option + 3"

On the right-hand, menu extras menubar, click on the flag icon and then select keyboard viewer. Press the option key and watch the dialabrian's answer appear in the numeric 3 key location.