It is well known that when emulating classic games on modern displays, you need to be careful not to distort the aspect ratio. Generally speaking, CRT screens were 4:3, and specific pixel aspect ratios of many classic arcade games, consoles and computers are given here.
Of course, title safe area was a concern, particularly for home computers that had to work on many different models of TV sets. It's hard to say exactly what was the title safe area for NTSC TV, but the Commodore 64 is generally accepted as having come pretty close to it. From the above table, 320 pixels / 8.19 MHz = 39 microseconds, which sounds in the right ballpark.
NES: 256 pixels / 5.37 MHz = 47.6 microseconds. That is significantly past the title safe area and into overscan, but that's fine, that was a feature for a dedicated console; it matches one's memory of playing Super Mario Brothers, where objects would scroll onto the right of the screen without any visible border.
Missile Command: 256 pixels / 5 MHz = 51.2 microseconds. Hmm. That is even considerably further into overscan. Resources are being wasted generating pixels the player will never see...
... unless. That's an arcade machine. It came with its own screen. Sure, TV picture tube minus the tuner, 4:3 overall aspect ratio. But maybe they could have tweaked the display electronics to shrink the horizontal scan, so more of that 51.2 microsecond active scan line is visible.
But in that case, the calculated pixel aspect ratio of 27:22 would be no longer valid. And in general, it would be harder to figure out exactly what was the pixel aspect ratio of arcade machines. Calculating it from the pixel clock in the same way as for home computers and consoles would no longer give quite the correct results.
Is the above conjecture correct? Or did arcade machines actually use the same parameters as TV sets, and did Missile Command just accept some extra wasted pixels?