Unknown brand Mark on clip. Need help identifying logo and pen

[jtodd5dot1]

Picked up a couple vintage pens at an antique mall, and got a mini pen/pencil set for Christmas.  Still trying to clean them up to identify, but this one is the only thing that has some identifier on the pen, which in this case is a logo on the clip.  The logo is appears to be an "S" using dashed lines, with a dashed line "O" above the "S" as well as within the loops of the S.  (photo attached).  First thought was Sheaffer, but the pen has nothing else in common with what you'd expect from Sheaffer.  Also, looks to be maybe a 14k gold plate nib that the gold is wearing off.  So I'm kinda at a loss.  Any thoughts for the internet hive mind?  (will add more photos to the thread of all the pens once they've been a little more cleaned up.

 

Thanks!