A genuine Penny Black VR official.
Bernhardt Assmus (Born c. 1855), originally from Hamburg, Germany, was a stamp forger operating in London. 
He was unmasked after
Morris Giwelb bought forged Penny Black VR official stamps from him in August 1890.  Giwelb accompanied the police on a visit to Assmus' premises at 12 Church Street, Islington, and assisted them at  Vine Street Police Station in sorting the seized material. 
References [ edit ]
^ "Police" in The Times (London, England), Thursday, Jan 07, 1892; pg. 14; Issue 33528.
^ a b "Morris Giwelb" by Cyril Permutt in Philatelic Paraphernalia, No. 23/24, April/July 1990, pp. 333-334.
^ Birch, Brian. (2012) . 12th edition. Standish, Wigan: Brian Birch, p. 880. Biographies of Philatelists and Dealers
Further reading [ edit ]
Herst, H. (ed.) (1986) Forensic Philately (An Account of the Famous English Stamp Fraud Trials involving Messrs. Bluett, Benjamin, Sarpy, Jeffryes and Dr. Assmus Originally Published in "The Stamp News", 1890-1892). Lake Oswego, Oregon: Herman Herst Jr.