Interesting device on eBay -- CDC clock generator?

[William Maddox on CCTalk via cctalk]

The seller thinks this may be a drum memory, but it is clearly not.   My 
guess is that it is some kind of clock generator.  Anyone recognize 
this?

https://www.ebay.com/itm/Vintage-Mainframe-Computer-Part-Drum-Memory-Control-Data/312942951497