I've not researched the Claus/Clause family but there is one rifle *attributed* to a Claus on the KRF Lehigh/Pres. Display 2010 disc, rifle #18. It's a funky rifle, looks basically like someone up in eastern Berks copied a Moll/Rupp style but added his own semi-drunken twist. Lots of wonky carving. I don't know the basis of this attribution but it's probably a ca. 1790s or early 1800s rifle. Also, there are a couple of old rifles around that may have been made by either the same guy or someone associated, one of them is in one of the older books maybe the 1750-1850 book I'd have to look; it's the weird piece with the 1794 (iirc) date in little brass studs on the toe line of the stock. I've talked to one or two people who consider that a Clause rifle.
Rich Hujsa talked to me about the Clause family a few times years ago but he's gone now and I don't think he had anything concrete i.e. signed. Tim Lubenesky might know something or some of those 'Allentown mafia' guys. I know I've never seen a signed rifle of these makers but I know I've read reference to one or two somewhere, just can't remember where.