The Volare is on my short list, but I don’t think it is 531. I do believe it to be a Panasonic made bike as were the original Voyagers from 1973-1975, and Voyager lls from just afterwards. High quality as mentioned. The Voyagers are around, but I’ve never seen a Volare in person. Back to the Super Sports, mine have all been in the 124-128mm rear dropout spacing. And also congrats on finding the B15 to be in good shape. It is my favorite Brooks and I think it may be just slightly softer that the B17s. Your observation on these being smooth riding is spot on. It is kinda strange considering that it is a stiff frame, and also has quite modern frame angles. Do look up the fillet brazing that these were manufactured with. They were hand done, and it is actually something to brag about owning. Put them in the category of a sort of GT gentleman’s style bike. Ride and enjoy.