Can someone identify the designer or manufacturer of this midcentury Danish chair?  

Helge Sibast? or Finn Juhl?

Is the center spindle missing in your chair, or is the design intended to have a gap here?
Chances of Finn Juhl < 0.1%
Sibast is a closer guess (by default, anything would be closer), but unlikely.

I'm with cd on this one, but moreso. Not Finn Juhl and not Helge Sibast. Both are too well known for such a discovery.
Helge did like spindle backs though, so there is that.

I believe it's part of the design since both chairs have the same gap. I could be wrong though. It does look like the size of the gap can accommodate two spindles.
I've been searching through furnitureindex.dk with no luck. God, if you're listening...HELP!!!
The search must go on!