The general consensus is that the 230 SL and the 250 SL had square weave, and that the 280 SL had loop. There are some questions about when in the 280 SL, it is not listed in the table of changes we published in Pagoda World.
I used the search term "square weave" but without the quote marks in the full search - using the "search " in the line of items beginning with "Home" - that searches the entire forum. I only scanned through the first page to see what was out there.