1) I have heard that the dial is actually smaller on the SD than on the Sub; I have not yet had the opportunity to do a side-by-side comparison. Is this true, and if so, is there a specific reason why?

2) I'm sure it's been asked a zillion times here, but what is the specific reason for the SD not having a Cyclops lens? Someone told me once that it something to do with the equalization of water pressure on the crystal when diving to extreme depths, but I don't know if this true. Frankly, I don't think I'd miss it much at all; the date is actually easier to read without it (IMHO) and makes the dial look much more symmetrical and less cluttered (almost like a 5512 in a heavier case...very nice).

3) How exactly does the helium escape valve work? Is it an actual mechanical device with moving parts or simply a steel "plug" machined to an exacting tolerence that allows helium molecules to escape? The earlier posting I referred to had a reply suggesting that the valve may require additional servicing if it goes unused...shouldn't it hold up as well as any other seals and gaskets in the case?

4) Do SD's hold their value better/worse/about the same as Sub-Dates? Do their much lower total production numbers make them any more desirable as collectables over time?