The John Sheldon from 1851 is age 29, so born about 1821/1822
This would be the wrong birth year, but of interest because of his father's occupation
John Sheldon age 2 born 22nd December 1819 baptised 1st January 1822 at St Philip, Birmingham, Warwickshire
Father: William Sheldon, Mother: Sarah.
Also baptised at same time Henry Sheldon born 21st May 1821.
All living in Hospital Street.
Father's occupation : Japan Waiter
This is one partial definition:
'JAPANNER One who applies a hard brilliant coat of any of several varnishes to objects'