Can you help me identify the antenna? Looking to add External Antenna

Do you mean the resistance across the coaxial connector, from the center pin to the ground?

Depending on the type of antenna, it should either be infinite (Most antennas, including pringles cantenna, which uses a simple 1/4 wave antenna), or a dead short (Some odd types, like a folded dipole).

Keep in mind that an antenna is just a collection of one or more conductors arranged so as to couple a certain range of frequencies effectively to free space.

As such, the only real limitations on power handling is the current-carrying capability of the conductors, and the voltage-withstanding capabilities of the insulating materials used in the antenna. Even a modest antenna can handle 60W with no problem.

Of course, in a typical wireless network application, you're never going to get close to these power levels, but there's no reason (i.e., cost savings) for the manufacturer to make the antenna any less rugged.