I have a C30A that I recently purchased on eBay. The original gasket was in fair shape but did not seal sufficiently to hold vacuum in the lower pot. Only about 2/3 of the brewed coffee would return. I ordered a new C30 gasket and O-ring from Dayseal.com.
My set arrived with obvious manual modifications to allow the seal to maintain the original depth. Once installed, it worked perfectly on my test 6 cup run. The C30A can brew 8 cups but that test will have to wait until my pulse rate returns to normal (my caffeine level drops)
Prior to installing the new seal system, I measured the top-pot height with a combination square. The original height was 9.75" for my C30A. Once the Dayseal system was installed as per the diagram on Dayseal.com, I rechecked the height and confirmed it to be the same with out any modifications on my part.
Here are some pictures comparing the original 63 year old neoprene gasket from my C30A with the embeded retainer ring (on the right) to the new Dayseal main seal. The as-received manual modification to the Dayseal are apparent in the photographs. Subsequent post will show the assembled height comparison and another picture of the inverted C30 Dayseal main gasket. I didn't include a picture of the O-ring - it looks just as you'd assume