Searching for information on the differences between the SL-1210 MK7 and SL-1210 MK2, I found this forum post and linked article (in greek). 

• Rotation Quality
  • Mk7: Excellent rotation quality (0.036% IEC, 0.036% NAB).
  • Mk2: Close but varied (0.297% IEC, 0.032% NAB) due to arm suspension tolerances.
• Rotation Accuracy
  • Mk7: High accuracy with modern direct driving but less precision than a micrometer setting.
  • Mk2: Similar high level with a slight difference (0.137%).
• Wow & Flutter
  • Both Models: Similar W&F variations over time, staying within [-2, +2] seconds.
  • Average W&F: Mk7 at 0.072%, Mk2 at 0.079%.
  • Peak-to-Peak W&F: Both at 5%.
• Frequency Analysis
  • Low Frequencies: Both show very low coordination levels at -60dB.
  • Higher Frequencies: Mk7 around/below -100dB, Mk2 slightly different but similarly low.
• Rumble
  • Mk7: Very low rumble with minor tuning spikes.
  • Mk2: Similar low rumble with minor frequency differences.
• Signal Reproduction
  • Harmonics: Both models show the second harmonic at -40dB, with Mk2 having lower noise levels up to 2kHz.
  • Higher Harmonics: Mk2 changes slightly above +6dB.
• Frequency Response
  • Low Frequencies: Focuses on 20-30Hz range.
  • Higher Frequencies: Minimal differences above 100Hz.
  • Acoustic Feedback: Mk7 has improved isolation, particularly in the 50-80Hz range, due to changes in materials and support points.
• Percussion Response
  • Both Models: Good compatibility with Denon's head, with Mk2 showing slight instability due to tolerances.
• Conclusion
  •  Both models are similar with small measurable differences.
  •  The Mk7 maintains high quality and performance, despite cost reductions, while nearly matching the older Mk2 model's performance.