Anyone specialize in Belgian Railway Parcel Post stamps? I have two copies of one from the 1938 series where the surcharge is a drastically different color. I'm just curious as to whether anyone has seen a reference to such a variant. The stamp in question is:
Michel PP12
Scott Q209
Yvert et Tellier CP203
Stanley Gibbons P807
AFA number PP13
Belgium TR203
Unificato PP203

Thanks for any insight anyone can provide.
Joe