OK… I’m prepared to be laughed at but here goes.
Back in the mid-80s I bought this in London’s Chinatown to hang on my wall (so I know it‘s not some desirable antique).
How would you describe it (preferably politely) and how should I go about selling it (if it’s worth selling)?
Now let's hope I attached this photo correctly...
[ Linked Image ]

Hello,

It would be called a Wakizashi, based on its shape (smaller than a katana). The type that you have is very common, these types of swords are referred to as 'wall hangers' or 'sword like objects', as they were made (generally in China, India, or Pakistan) to look nice decoratively but not for any real/functional purpose. The value is <$20.

The question though is the fact that you said you purchased it in London? Are you still based in the UK? In the UK it would be illegal to, sell, hire, lend or give the sword like object to anyone. It is a banned knife/weapon https://www.gov.uk/buying-carrying-knives You are not committing an offence by owning it, but by transporting it anywhere, or selling it or transferring it in anyway can result in prison time or hefty fines.

Hope this helps!
Z
:)