Were those new? I was told that the C-# was the date code. C-04 would be 2004. It looks like a mixed set, I could be wrong.
Also, I've seen Jesel aluminum look like that. Aluminum has a finite life in this application.

I had a set of Harland Sharp shaft rockers that broke the same way. After I did some research and found out it was a common problem with them. They had low hours on a street car, less than 500 with most at 2100rpm or less. They did inspect the set and replaced the broken rocker. This was a $1200 set. I never bolted them back on the heads. I tried to save a few bucks over a set of T&Ds. Cost me more money in the long run. I am running the T&Ds now for 10 years without any problems at all. I just sent them back to T&D for inspection as I am rebuilding and upgrading the engine. The rockers all were in great condition. They recommended changing the roller tips so I did.

There is always time and money to do it right there second time.

Just my .02

You might consider the Crower stainless

I just recently used 3 sets of scorpions, 2 on iron 880 heads and 1 on edelbrock rect ports. I was able to get perfect geometry on the iron heads, on the edelbrocks it was sketchy and far from perfect no matter how long or short i adjusted the checking pushrods. I would have tried something else to see if i could get it more ideal but customer bought them and was set on running them no matter what, i got the geometry the best it was going to be and callled it good,fwiw, Smitty