It's definitely not like a bumper... thanks for that reference, really makes it quite obvious.
I think it's sleeved too, were any Listers in the era 1960 sleeved from the factory?
I feel convinced it's not chromed, now the question is, should i go with chromed rings? Seems like with chrome rings the bore would wear and I'd have to bore or sleeve before having to change the rings again but if i had to do that I'd probably change the rings anyway so what's the benefit?