I downloaded the iPhone app and did some testing. The same test record that I used before also has a track with 3150Hz. As I mentioned before, I measured considerable runout in my test record which by itself causes some audible Wow when playing constant frequency test tones. The center hole of this test record has a slight amount of play on my tt spindle. After much patient work to minimize the record runout I got the following measurements: Mean Freq: 3151.3, Raw Frequency: -0.22%/+0.24% relative, -7.0Hz/+7.4Hz absolute. Lowpass Filtered Frequency: -0.02%/+0.01% relative, -0.5Hz/+0.5Hz absolute. I'm guessing that the filtered values subtract out the record runout. The reason I conclude that is as I meticulously adjusted the record on the platter to minimize runout, I had raw numbers as high as -9.8/+10.7Hz while the filtered values never exceeded 0.03%.
Another observation: The original Mean Freq was 3155.6Hz based on my setting using the strobe disc. I adjusted speed down and can certainly work some more to dial it in at precisely 3150Hz. The other observation is that holding the iPhone while taking the measurement adds more error. It is sensitive enough to pick up hand movements. I set the phone on a table about 1 meter away from the front of one speaker.
So how does my humble BD table compare to some others?
btw- I have a record clamp. So I adjusted the record relative to the spindle and then clamped the record down.