From Ostende to Verviers in 1920

This express cover sent from Ostende to Verviers on 1 April 1920. It bears a very nice corner block of 6 with full margins and plate number.

Characteristics: 15c+15c in block of 6, margin corner Total franking of 90c Express cover
Estimated value: $110 [Auctioned on Delcampe.com in April 2007]