Germany 1880 10Pf Michel No 41ab (x3) UV Fluorescence - On Registered Cover

Provenance: From an authoritative and scholarly collection of German Postal History purchase at auction in the UK.
Note: My UV photographs are illuminated by a HQRP torch. The fluorescent colours noted in the printed description have not been certified.
 
Please examine the photographs and read the postal rationale of this cover.
Condition is excellent.

Please examine my listings for numerous excellent and scarce covers.(F6) AG821