Touching up paint

[OhToBeASeahorse]

I need to paint a bit of a wall where a socket has been moved. But - stupidly - I can't remember if we used silk or matt and I can't tell!
Is there a fool proof way of checking and if not which is best to go for?!

You can usually tell by looking at it.

You can write on matt with a pencil, but it skids on silk.

If it's slightly shiny it's silk. If it's very slightly rough to the touch it's matt.

I reckon its silk after close inspection with a torch!