This is a nice clean 8 inch long divider made around the turn of the century by a rarely seen maker P. Lowentraut which is marked on the side of the tool, also marked is "LOWENT...T MFG. CO. NEWARK N.J. MADE IN AMERICA U.S. 8". Made of brass at the joint and steel elsewhere.  It is adjustable by tightening the tightening screw on the wing after moving the points to the approximate measurement desired, then fine adjusting it with the round knurled nut on the side. Works great, a nice clean tool, no rust!  We note that the tightening screw on the wing is most likely not original but hold on the wing with no problems.