Hi Brian,

Indeed, neither the edge nor curve that resulted from copy/paste of the edge are arcs:

The edge's Details are: Open edge, Joined, Planar

The pasted curve's details are: Open curve, Planar, 1 segment

And a real arc's details are: Open curve, Arc, Planar, 1 segment

From the API perspective I believe the relevant properties are isCircle and isArc.

Odd though that a boolean diff with a sphere as cutting object wouldn't have left an arc behind but I suppose it depends upon the object being cut.

> How does MoI know if a curve is an arc?

It's Halloween, so it must just be magic... ;-}

--Larry