i think the Clarks inner diameter is about 0.2mm shorter than gen spec, and the outer diameter is about 0.3mm wider than gen spec, so when the the crystal is initially pressed on, prior to the retaining ring, it is already way too fat. So once the crystal is on the case, it is about 0.5-0.6mm wider than the inner diameter of the retaining ring. Normally, the retaining ring should slip on about 2/3 of way down the crystal prior to pressing, but in my most recent experience with the vintage T19 Clark's, the retaining ring just barely fits over the crystal shoulders... I think these recent batch of clarks are off compared to the Clark's I've used a couple years ago.