Thank you all for the kind welcome and your help with my question.
I probably should explain that this knife is a user. And, I'm pretty sure it's carbon as there's a fair bit of patina on the blades. It sharpens and holds an edge really well too.
There's nothing on the tangs to indicate what steel they're made of though and it's always intrigued me.
I'm afraid the box and paperwork were filed in the bin as soon as I got home from the gunshop where I bought it way back in the 70's

. Back then a knife was 'just' a tool. Geez I wish I'd bought a whole load more of these then and put them away safe

. But as they say hind sight is a wonderfull thing.
Tony