Immigrant Arrival Question #usa

Lawrence Weintraub

My grandfather, Samuel Edelstein (Hebrew name Zechariah) lived part of his life in Boston and filed his Declaration of Intention there on February 16,1920. On it, he claimed to have landed in NYC on February 22, 1902 from Stepan, Russia sailing from Hamburg, ship unknown. He later moved to NYC permanently but never completed the citizenship process; still listed as "First Papers" on the 1940 Census.  I have tried to research the actual ship and date, to no avail.
Later arrivals like my great grandmother and a young great aunt and uncle travelled as "Proshkulnik" but magically became Edelstein once touching land (in Boston). I have assumed that to have been her maiden name but that Samuel travelled as Edelstein.  Can anyone provide guidance on fleshing out Samuel's arrival information?
Thank you,
Lawrence Weintraub
Old Bridge, NJ

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