the naming of things

I have a pair of anvil secateurs (see Felco explanation) with a ratchet mechanism. I am pretty sure their spring has gone. I therefore want to take them apart and replace the spring; so far so good.

However. None of the guides, or indeed spares kits, I have been able to find... actually include A Key Part, the name of which I do not know and have thus far failed to generate a competent search term for. Ordinarily I'd bimble down to the local Screwfix (or indeed drop by Mackay's next time I'm in Cambridge) and ask for advice, but, well.



The point of contention is the wee black ?flanged ?washer in the centre of the image, at the top of the silver-black-silver sandwich. It's holding a pin in place (by dint of the pin having a slightly broader end to its shaft). I am capable of using calipers to work out what size I need, but I've tried variants on "retaining clip" and "flanged" and "washer" and even "circlip" (which is an entirely different thing) and have got nowhere.

I would be extremely grateful to be told its True Name!