The 16610 sub is the most popular model and it seems everyone has a TC sub these days.
The one thing that I like to do is to swap a gen crystal. I recently purchased a Clark crystal to try it out as the previous clark crystal was 2.0mm which is not gen spec anymore for the modern sub. This new version is 1.8mm. That means you can replace a gen crystal or a TC crystal and the height of the crystal will be the same afterwards.
The edges of the glass are well polished. The date mag appears excellent, not overly magnified. Clarity is great. Cyclops is applied well and level and is in the correct position. I think this is a good alternative to the gen style subs where the rep LEC is too pronounced or there are other concerns about the rep crystal. Nothing beats a gen but this is real close.
I tried to label the pics, clark crystal is set to date 24, gen is set to 28, gen is always on the left with 2 crystals in the picture.
To keep things fair, both crystals are mounted on the same gasket which happens to be a 2.7mm gasket in this case. The date mags are really close.
For those who dont know, Clark is a respected seller on ebay, I have no relation to the seller http://stores.ebay.com/clarkwatchparts/