When I first saw a pocket watch crystal with a concave dimple , I just assumed it was gouged by an unfortunate accident. But I later found other examples with the same pattern... and I really can't explain them. I only ever find them on older pocket watches. Thoughts?
http://www.pocketwatchrepair.com/how-to/crystals.php Apparently they are called "High-Dome Bullseye Crystal", either English-style (earlier, late 1700's-early 1800's) or American (later - early 1900's). It also seems nobody knows for sure what their purpose is...
I suspect it's something to do with the manufacturing process, like antique crown glass window panes.
I don't believe there is a consensus on the nature of the Bullseye crystals. Some believe it is an artifact of the manufacturing process, and some believe it was just a style that was popular. I personally don't believe that it was part of the manufacturing process - I have yet to see a convincing argument supporting that idea. I think it was just a style. Cheers, Al
Seen that explanation, but still not convinced personally. If the stem were used to spin the glass and grind it round, then I would not expect to see so may off center bullseyes...
Nah, I'm not going for the spun-glass explanation, either. I've owned a wristwatch from the '50s with this type of crystal.
I too have seen these and simply assumed they were a "fashion" carry-over from the half hunter cases?
I don't think that anyone is claiming to be an expert, but why on earth would such an anachronistic and expensive process have been used as recently as the mid-20th century?
I understand completely the process involved in glass blowing, and have many objects of blown glass with the pontil mark. That really isn't the problem with this explanation - what no one has satisfactorily done in my opinion is make the direct connection from glass blowing to the crystals shown by the OP. As Tony points out, making crystals this way in the mid-20th century doesn't make a lot of sense. Until that can be explained somehow in a more concrete way, I'm not ready to accept that as the reasoning for this style. Cheers, Al