JCB
Not that one although it looks like the one my eye doc uses, B&L makes a 3 1/2X arounf 2 " dia loupe.I have one and it has about 3 " focal length. Stop by some time
This may or may not be of any usefulness to you; kind of like monk, I too find lenses from old telescopes, old binoculars, and old spotting scopes; even new inexspensive binoculars from Walmart are useful. They're fairly easy to disasemble, and combinations of different lenses makes very useful loupes. You can find them at yard sales; I mostly find mine on eBay. I use a small lathe to make tubes to encase the lenses, and then wrap them in leather, just like a mini-microscope. Hope this is of some benefit. Good Luck.