Vertical resolution is easy. RS-170 video is 525 horizontal lines, even lines on every second field, odd lines on every first field.
The horizontal resolution cannot be known. Here's why:
Originally the video standard was simply black and white. A single beam swept across the screen creating light and dark segments. Now, there's no mask, no stripes of phosphor, so the resolution was, in essence, infinitely variable. This standard, now known as RS-170, has its resolution defined thusly:
Horizontal resolution depends on the camera and other video system components. Since it is an analog signal, the exact number is not critical; it just limits the detail that can be resolved. The horizontal resolution of an analog video image is limited by the signal quality, as determined by all hardware--the video camera, storage medium (if used), intervening cables and circuitry, and display technology. Black and white cameras and CRT display tubes can resolve detail approaching or exceeding 1000 video lines. Typical resolution specs are on the order of 400-700 elements per line. This empirically defined quantity is the number of pairs of black and white parallel lines that could be counted across the display monitor at the limit of detection by a human observer.
So, basically, based on a number of unknown things, the resolution could change.
Now, NTSC video (RS-170a) uses a 'colour burst' before each line, basically a high-speed sqiggle signal that applies colour across the entire line. This colour resolution is lower than the black and white resolution, as a matter of necessity really: less time is given to the colour burst than the rest of the line. So the question is now: Which resolution are you asking about, the black and white hi-res signal, or the low-res colour signal? VHS cassettes have a horizontal resolution of like 30 pixels, and that would vary based on the colours involved! LDs could do about 120 colour pixels, and S-video could do about 140. Modern gear makes these numbers a little outdated, but still: what number do you want?
Colour TVs, with a finite number of coloured phosphor strips, have an upper limit of resolution, but even then the peak input res probably doesn't match the TVs capabilities, so what is the resolution: the input res or the max capable res on the screen? And which screen? Larger screens had more phosphor elements than smaller ones, but could still display the same image. Really small screens tended to lose more to overscan, and how do you count THAT?
There's no standard horizontal resolution. There can't be
. So your question, I'm sorry, cannot be answered.