Heir Designate is an Heir that was promoted to that status as opposed to having been popped as an Heir.Erf-b1-p079, Erf-b1-p082
Promotion to Heir Designate rarely occurs and is very expensive.Erf-b1-p079
Known Heir Designates
Caesar Borgata was a Viscount, a minor Noble, but was named Heir Designate after Don King's unfortunate previous experiences with heir-popping.
The only known non-Noble Unit promoted to Heir is Stanley.
Aquring an Heir is in general extremely expensive, either in Shmuckers (Heir Designate) or in production (Heir).