Hi Guys
Finally managed to add a British MK3 helmet to my collection recently . When I got the helmet I tried to find a manufacturers stamp to find out when it was made and by whom. I have three MK4 helmets so I looked in the same areas in the bowl part of the helmet where I found their stamps with no luck. I heard that some MK3’s didn’t have a stamp or it was unreadable due to it being hidden under the paint so I concluded that mine was one of those.
But determined I had another go and managed to find it. It was on the inside of the rim near the front edge, a place I didn’t expect to find it. I needed magnifying goggles and a torch to see it because it is very faint and only partially readable. It’s a RO&CO stamp.
Posted this in case anybody else hasn’t been able to find their stamp to illustrate where it might be. Here’s a picture of it, I had to highlight it with a pencil to make it visible.

British MK3 manufacturers helmet stamps