I have been loving my 512 and looking for a new strap. I love the JV but they don't make it for the 512 in 22x20. Doing some searching I found this. I know David very well and unfortunately he sold the watch a while ago. He is going to try to find out what strap it is but he knows it was OEM.
The strap looks very close to a JV. Did Panerai make one and now it's discontinued? Is it something different that just looks like the JV? The only other thing I could think it was is a cut down JV to fit. If it's cut down how hard is it to do that.