This name is a synonym of Magnolia × loebneri Kache.
The record derives from WCSP
(data supplied on 2012-03-23)
which reports it as a synonym (record 117664) with original publication details: J. Arnold Arbor. 57: 297 1976.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:886605-1.
This name was in version 1 of The Plant List, record kew-117664.