I agree with Carrie on the dating although your pieces could be early '60's. I'm not sure they are a "set" although they certainly compliment each other. The design elements are a little bit different. The missing stones will be easy to replace.
Many manufacturers stopped setting stones by hand in the later '50's and stopped finishing the backs with a smooth finish then, too, to save costs. Not every comany used the © mark on every piece so while that's a good rule of thumb on dating to pre-1955, it's not set in stone. I just looked through my photos and I sold a Hattie Carnegie brooch that does not have the © mark on it that I believe is early '60's.
I still have this funky Hattie Carnegie brooch. It's japanned, and signed on a cartouche with no © mark.
With these colors, I'd date mine to the late 1950's early '60's - which is when jappaned pieces were popular.
Hattie Carnegie died in 1956. Jewelry with her mark was still made as late as 1979. She didn't design any of the jewelry (or, so I understand the clothing either - although she did employ a lot of designers and did the design editing during her lifetime). I am pretty sure that the Hattie Carnegie comany did not manufacture jewelry. Jewelry was either made for the Hattie Carnegie company, or purchased from a jobber. It was made at various price points. Frank DeLizza (who made the jewelry we call Juliana) made some Hattie Carnegie pieces. I would be interested in seeing the back of the bracelet and the dimensions, also.
So to answer your question, KK - some Hattie Carnegie jewelry is more desireable and better made than others.
Probably more than anyone wanted to know!
Linn