cover 12Kr. lilac and 6Kr. yellow-brown (olive shade) both, fine with good margins on 1870 buff envelope to London via Forbach, neatly cancelled by single-ring "RODALBEN 28/5" d.s. with another strike and transit c.d.s (in red) adjacent, and arrival c.d.s. (30/5) on reverse. A very rare franking of outstanding quality. Signed Pfenninger. M.18 + 17. Photo in colour