Dunlavy SC IV extra tweeter felt?

To dampen it. Most likely, the origional tweeters needed to be replaced and the exact same ones couldn't be found. So they installed new tweeters that were close, but not identical to the origional. The felt pieces were probably used to tune the new tweeters in an attempt to make them sound more like the old ones.

"So if the OP's tweeters have any felt attached to the domes then as Zd542 suggested, it was likely done on replacement tweeters rather than original. Four felt pads, even if very small, seem likely to damp/reduce HF response by a significant amount.
Pryso (Threads | Answers | This Thread)"

Yes. That was exactly my point. When I looked at some pics of the OP's speakers, I couldn't find any that had diamond shape felt anywhere near the tweeters. Not to be confused with the wool perimeter for reducing reflections. They were all in place. Since the company is no longer in business, I thought the diamond felt pieces were used to mod a tweeter that wasn't exactly the same.

"03-12-15: Pryso
I wonder if there might be some confusion here about whether the thick wool felt was utilized to closely surround specific drivers or actually attached to the cones/domes of drivers?"

In this case, it was both. If you look at a pic of the speakers, you'll see the tweeter surrounded by a felt/cloth type of material. It doesn't touch the tweeter, it just surrounds it. The OP was talking about actual pieces of felt attached directly to the drivers themselves.

"03-12-15: Rleff
Zd542 if that is the case then my scIII's had the felt only surrounding the driver and not actually attached to any part of it."

My comments were just to try and make sense of the OP's speakers. I thought that since Dunlavy was no longer in business, people may have had a hard time getting replacement parts. Since no one can find an instance where felt was applied directly to the driver, it was my guess that someone would do this to "tune" a close match, that was not a direct placement. I could be wrong on this. It just seemed like the most likely explanation.