I have been watching these cracks in the acrylic crystal grow and develop over the last month or two. They started off as a small cluster of half a dozen localised, tiny fractures which have slowly grown and joined up until they are two large cracks. Before I dive in to replacement of the crystal I am trying to find out more about the failure mechanism to reduce the repeat of recurrence.

I am not sure what has caused them but I am fairly sure there wasn't an impact as there are no gouges or other signs of damage on the surface. I also think I would have noticed a knock hard enough to crack the crystal. To my untrained eye, at the beginning, they looked like tiny stress fractures deep within the acrylic. Is this a common occurrence in acrylic crystals

My vague theory is that the original crystal had been replaced but, in the absence of the correct size, a slightly oversized one was squeezed in. This set up of stresses within the crystal which were increased, perhaps with the case expanding in the heat of summer. Is it possible for an acrylic crystal to fail like this or am I over thinking it and it's a case of shoddy workmanship?

Moving onto the subject of a replacement, I know that Eddie no longer has spares and that the diameter is 32.4mm. I am not sure of my terminology but I am guessing the style on the PRS-29A is a box crystal. Are all acrylic box crystals all created equal or am I better off buying one from a particular source? Do I need to buying anything else like gaskets etc?

I expect that I'll end up sending it to one of the forum's resident watchmakers as this is one of my favourites and I would be peeved if I ballsed it up but any answers to the above questions will be gratefully received and noted for future reference as I am keen in to improve my tinkering skills.