Christoph Gaertner Philatelie has this 1s green and carmine on cover in their next auction. Not only are these scarce on cover (just over 50 are known), this is possibly a unique usage, as it was sent at the AR (advice of receipt) rate, with two strikes of the “AR” handstamps adjacent. The starting price was €400, but was unsold. Perhaps because the 1s isn’t particularly tied to the cover, but it does seem to be genuine.
Gaertner has scarce 1s green and carmine on cover
Filed under Auction News
The 1887 Jubilee Issue 
Gaertner has offered this cover again in their June 2011 sale, lot 5117, starting at €380 and again was unsold
Gaertner has offered this cover AGAIN in their August 2011 sale, lot 6984, starting at €350
Hurrah! They finally sold it for €370!