I have a theory that the frame is damaged, I am sorry to report. The wrap-over stays on these models is just a single piece cast steel, a time saving device on lower-end models. It tapers to a thin radius and then tapers back out on the other side. It allowed frame builders to wrap over the stays quickly at any angle, no matter what size is the frame. If you take a really close look at the wrap-over stays, you will see that the cast item is positioned to point downwards STRAIGHT TOWARDS the dropout. While it's atop the seat lug, it points that way. But just as it ends (it's only about 1.5" long and slips into the seat stays at the middle of the "C" decal), the seat stays change direction and head more towards the chain stays or bottom bracket. If you were building a frame from scratch, it would NOT change direction like this. If you were buidling a frame like this, the wrap-over would be pointing more downwards and there would not be a change of direction between the wrapover and the start of the seat stay tubing. The good news is that I am certain this in no way affects the soundness or ride of this frameset.

As far as I'm aware Carlton never shipped a bike with curved stays. I own 20+ Carlton bikes including a 1950 Carlton flyer which has a wrinkle right beneath the seat lug all the way around because someone put something too heavy on the seat, compressing the seat tube, once upon a time. I think something similar happened here - maybe someone hit the saddle while the bike was atop a car on the way into the garage or something similar.

If my theory is correct you will be able to find wrinkling int the paint or chrome somewhere along one of the seat stays.

By the way I once owned the very same type of frameset - 2030 carbon steel, wrapover stays, 23.5" size, 1973 Raleigh Grand Prix. I once shifted the Suntour V-GT derailleur into the spokes at 30mph and locked up the rear wheel. After slipping and doing a foot touch-down on the right, left, right, left, I managed to stop (my rear wheel had stopped instantly, skidding the tires), and my right rear seatstay had quite a bend near the dropout of about 12mm inwards from the tremendous torque applied by the force of the ground and the drivetrain as I was pedaling like mad when I shifted the gears into the spoke, causing an instant rear-wheel-stop. So a similar type of frame damage can happen to a carbon steel frameset like this. My frame was pulled out (just the right-side seatstay was bent in - not both - and in a much more localized place) at a bike shop with a wire-pulled tube-straightening tool, I think VAR made them. Since your frame is truwell tubing you might have exceptionally (too) lightweight seatstays, it was a type of lightweight bike called a club racer which was later outlawed by the CPSC, making this type of damage more likely from a rear wheel lock-up (without the furious pedaling as I was doing). Alternately, maybe someone weighing 350 lbs sat down hard on the seat, but got up before the frame was pretzled completely?