The Next Generation. Leitz Summicron 50mm DR

This is the third in the Marking Gauge Series.  Back in the '90s, the innovative Canadian toolmaker, Lee-Valley/Veritas began producing marking gauges that use a cutting wheel instead of the traditional scribe.  It wasn't their idea; the owner collects antique tools, and from time to time Veritas puts into production a replica of an item from his collection.  Or sometimes, they'll do a riff on an old idea, improving the original concept.
The thinking is this: the scribe on the old tools leaves its mark by tearing the wood fibers.  The cutting wheel works by severing the fibers.  This is particularly advantageous when marking a line across the wood grain, since there is no tear-out and unsightly scarring.  When the wheel becomes dull, it can be unscrewed and a nice sharp edge reground.  I bought this gauge back in the late '90s, and, under the intense mag, it becomes clear from the nicks and dings that it has worked hard for decades.  I keep it set to 3/4", or 19mm, a thickness of wood often used.