Genuine

Genuine overprint 11 1/2 mm long; Perf 12 1/2 or 13
Reprints are on white paper; Perf 13 1/2; Overprint 12 mm long

Forgery

Can be on genuine or fake stamp (see Macao)
Fournier is 11 3/4 mm long
Fournier cancel CORREIO 12 NOV 85 DILLY

Bibliography

The Work of Jean De Sperati by the British Philatelic Association 1955

Album Weeds by Rev. R. B. Earee

The Serrane Guide by Fernand Serrane

The Forged Stamps of all Countries by J. Dorn