There's no way a digital HF caliper is going to cut it. The resolution is only a half thousandth, and the accuracy (and that's advertised accuracy) is one thousandth. It's good enough to toss in your tool bag to take to the junkyard and tell the difference between a .68 wide rotor and a .72 wide rotor. Not nearly good enough to take measurements off the needle stations however.
A couple years ago, I measured some (what I believe are) N-27 needles. They came out of a pair of round top carbs I bought. I didn't own them from new and I have no idea how many other hands had been into them messing around with things. I may have been the first person in there, or the tenth. The needles may be OEM stock, or may have been replaced and changed many times. And unfortunately the numbers on the side of the needles is no longer readable.
What I can tell you is that the carbs appeared to be unmolested and the needles are N-somethings printed in black ink (not stamped into the brass). I can also tell you that the car I had the carbs installed on ran great with those needles. Not too rich, not too lean. The carbs worked great. Bottom line is that I believe, but cannot guarantee, that they are N-27 needles.
Lastly, I have a good eye, a steady hand, and made these measurements with a quality micrometer. I'm not infallible however, so would I would claim accuracy only to maybe plus/minus maybe two tenths.
So with multiple qualifiers and caveats, here are my numbers: