Mark's contact in London in 1920 was a brother B Cooper. Here is Barnett's information, including his arrival in the US in 1925 headed to his brother Mark in Detroit:
UK Certificate of naturalization to an alien
12 April 1912
Whereas Barnett Kipperhoor known as B Cooper, alien, residing at 111 Amhurst Road, Hackney Downs, .. a subject of Germany, having been born at Breslau Silesia on the 20th August 1883, and is the son of Hyman and Annie Kipperhoor, both subjects of Russia - a hairdresser and tobacconist ... etc, married with 2 children
stamped 26 April 1912, on the next page
-------------
1911 at 111 Amhurst Rd NE, Central Hackney
Barnett Cooper, hairdresser and tobacconist, born in Germany
wife Sarah and 2 children: James and Evelyn
-------------
London Electoral Registers
Barnett and Sarah Cooper
78 Fenchurch, (abode: 22 Seagry Rd, Wanstead E)
--------
US - Petition for citizenship
22 September 1932
Barnett Kipperhoor, known as Cooper
residing 5832 Sansom St, Philadelphia, a salesman
born Breslau, Germany, 20 August 1883, race: Hebrew
declared intention to be a citizen 23 September 1925, US District Court, Miami, FL
arrived in the US as Barnett Cooper (Barnett Kipperhoor) from Southhampton 23 May 1925 on the Berengaria, last foreign residence: London
wife and 4 children born in London, all live with him in Philadelphia
signed Barnett Kipperfoor
-----------
24 May 1925 arrival at New York, on the Berengaria
Barnett Cooper, 41, a hosier, Hebrew, last residence: London, born in Breslau, Germany
nearest relative in England: brother M Cooper, 8 Compayne Gardens, Hampstead
destination: brother Mark Cooper, 1998 Clairmont, Detroit, Michigan
accompanied by wife Sarah and 4 children including oldest son Hyman Augustus
----------
1930 Census
at 5832 Sansom, Philadelphia
Barnet Cooper, Sarah, and 4 children
-------
So that puts Mark's parents in Breslau, Germany/Poland, in 1883. I don't remember who ruled Poland in 1883, but I know it went back and forth between Germany and Russia a few times. So the parents being "Russian" would not be a contradiction. Or they were originally from further east in Poland and under Russian rule. You'd have to get into a history of Poland in the 2nd half of the 19th C. to find out.
-----
Chances are very good that if the records survived you can find Hyman and Anna (Rotstein?) Kipperhoor in Poland/Germany/Russia. Jewish genealogy research is fantastic.
