See this tweet from Helder Gil, who delights at reviewing and tweeting out the contents of the DC Register:
Zoning Com’n filing notice to redone 1326 N Capitol St NW from MU4 to MU5A; allows taller bldgs & more density. http://www.dcregs.dc.gov/Notice/DownLoad.aspx?NoticeID=6234789 …
9:19 AM – 22 Oct 2016
Here is the conversion of the zoning classifications from the old zoning regulations to the recently enacted new zoning regulations:
So MU-5-A is the old C-2-B.