That looks very old and likely past its use by date!
I wouldn't use it
@Neena was just about to say this
I would agree with @Heather
I wouldn't use that. If it's an unknown brand how can you be sure you're fitting correctly or that your child fits it without the instructions. It could also be passed it's safe use period
That looks old and tatty, I'd definitely be buying a new one for peace of mind
I’m assuming if you don’t know the brand or make of it it’s second hand, in which case check the expiry date on it.