to Col. Robertson, Waterford, Ireland, cancelled by a fine strike of the "EXPERIMENTAL P.O./C-7/MY 5 89" single-ring d.s. An extremely rare item from this obscure military operation. Photo" /> cover 1889 (5 May) 1½a. stationery card with message headed<I> "S.F.Force Gnatong"</I> to Col. Robertson, Waterford, Ireland, cancelled by a fine strike of the "EXPERIMENTAL P.O./C-7/MY 5 89" single-ring d.s. An extremely rare item from this obscure military operation. Photo | Christie's