Definition of VDO

I noticed that in the Barton organ there are stops labeled VDO and VDO Ext. Could you let me know what it means since I have not been able to fiind a definition. Also, what category is it (Diapason, Reed, Tibia,etc.)?

Russell

VDO is an abbreviation for Viole D'Orchestra, which is usually a skinny string stop, which has a bit of an edge to the tone.

Thanks for your reply. I had searched for the definition extensively to no avail. I really appreciate it.

Russell