This is a really nice, quality 20 inch long fully opened steel zig-zag or folding rule in very good condition overall!  This rule has nicely fitted brass ends, and the pivot pins are also brass.  The joints are all snug and the design of this rule with the convex shaped form really holds the joint locks in position well when fully opened up, or closed!  The graduations are in inches, very clearly marked, easy to read.  The first one inch is in 32nd grads. and the rest of the 20 inches is in 16ths grads.   We have seen other folding rules made in Germany in the past, but have not seen or had one of these for sale before in over 15 years in antique sales.  I would consider this one to be rare!