Not sure what you are after. DRAM is advertised to run at it's advertised specs....period. Even then, to run at spec it's up to an individual to ensure that they even have a mobo and CPU that is capable of running at a given freq....i.e. you see people quite often get DRAM that their given hardware just can't run at it's specified freq. I know of NO manufacturer that guarantees that their DRAM will OC over and above it's specifications to a higher spec....For most any sticks, a knowledgeable builder or user will look for things like low CL (as it's often the norm to have to raise CL as you OC), you often look at voltages for the same reason, to OC you often need to increase voltage over and above the spec.....Again much of OCing comes down to the individual....I've seen times where 2-3 people can take a single set of sticks (say 1600) and OC them 2 steps or even more and another person can't OC them at all (knowledge and skill), and I've seen the exact opposite where 2-3 can't OC a set at all, yet another can come up and run the sticks much faster...
As I've mentioned in numerous threads, DRAM is one of the least understood components in a rig, which is why I try and offer additional info on DRAM whenever I can....look through the forums, there are tons of people that advocate simply mixing DRAM and claiming it will be just fine when in fact in can be and often is problematic, and again, just peruse the forums, there's all kinds of threads about people who do this and have all kinds of problems. Many still believe if a mobo can handle the DRAM then you are fine, when it's actually the MC that is more the determining factor, again, look at people (especially with AMD) that buy a mobo that advertises 133 or 2400 and then wonder why their 2400 won't run and find they have a 955 or 965 CPU or something of the sort that is doing good to run 1600-1866.
When it comes to DRAM and OCing it above and beyond, there are no guarantees (as said), though in the forums you can often find those (often builders and computer techs) that work with enough brands/sets/freqs/etc of DRAM that have a good idea of the OC potential for various models of sticks...and there are things to look for (with RJs, this letter designation can give you an idea), you will normally see the H sticks having a lower CL, they might also use different chips than similar models...in short there's many things you can look for, research is a good thing, many put no effort into it at all as they simply don't know DRAM