General researches

Key(lock) - Wikipedia

https://en.wikipedia.org/wiki/Key_(lock)

V&A - Lock and key information

https://collections.vam.ac.uk/item/O350453/lock-and-key-wilkes-john/

The History and Future of Locks and Keys

https://gizmodo.com/the-history-and-future-of-locks-and-keys-1735694812

Is the traditional metal key becoming obsolete?

http://www.bbc.co.uk/news/magazine-29817520

Copy a Key by Casting

http://www.instructables.com/id/Copy-a-Key-by-Casting/

Casting Key Copies

https://www.youtube.com/watch?v=bWUhav3relw

Symbols and their meaning: the key

https://www.jweel.com/en/blog/p/2015/symbols-and-their-meaning-the-key/

The lock of love: padlocks on the bridge

https://www.theguardian.com/lifeandstyle/2016/feb/14/the-lock-of-love-padlocks-on-bridges

Key Symbloism

https://goodlucksymbols.com/key-symbolism/