Not many manufacturers depict the power source on the names of their products.
Personally, as far as some of Surefire's numberings go, such as 3C, 6P, 9N, the number means the voltage and, in turn, the amount of batteries that the flashlight operates on. As each CR123A (which Surefire pretty much invented) delivers 3 volts, 3C uses a single CR123A, 6P using two and 9N using three.
EagleTac is one of the few manufacturers that does it for some of its lights. E.g. - If you see A or A2 at the end of their model name, that means that the light will run on one or two standard AA formats, respectively. Same thing with a and a2, except it means AAA format. If you see C or C2 at the end, that means that they feed on one or two lithium CR123A formats, also respectively.