On these PT bracelets made for the Perpetual, the folding portion is often WG, but on some bracelets (like mine) the folding portion is PT. I was talking with another collector about this. I'm not sure which version was made first, the WG folding clasp or the PT folding clasp.
The other thing I didn't try, but was curious about, is if this bracelet would fit on a Lange 1. The Lange 1 and Langematik Perpetual share the same case diameter (38.5mm) and lug width (20mm), but the Perpetual case is 0.2mm thicker, and there may be other small differences in the lugs (such as where the holes are drilled). I'm not sure.