Vintage Zeiss-Ikon keyblank stamped 'OU' Nickel Silver GMK? Free Shipping!!

Description

Can't find any info on them. Not listed in Ilco, Silca or Jet Key Blank Referances. From what I can make out of the Zeiss-Ikon blanks in Ilco's reference, it looks to be a top level Master. Looks like a cut-away of the 60UA or the 60.IK. Hard to tell with a monitor.
Has 'OU' stamped on the reverse side, you can see it in the photos.