...these are typical of the construction details, and some changes over the years, on what I've seen. (Which is not a large number of them.)
The green one is the oldest of the three, with the red frame with newer head badge the most recent in construction. Maybe 15-20 years in range.
Your badging is of the earlier, diamond variation. Eventually, I think they went to just a "C", with rainbow stripes.
As mentioned above by someone, this seems like a pretty small frame. So maybe the custom construction needed something that a standard head lug wouldn't fit ?