OnTheTrail on Family Tree Circles

John (or Johan) Leonard Strombach (or Stromback or Strombeck) arrived in Dunedin, New Zealand as a crewman on the "Dover Castle" about 1873. On the crew list he was listed as John Strombach, Aged 22 of Sweden, having previously served on the "Czar" of Greenock (and prior to that on North Sea brigs and schooners). Against the entry of his name on the crew list he made his mark (a cross) which would indicate another person (perhaps the Captain) wrote his name, creating uncertainty as the correct pronunciation and spelling.

On 16th April 1874 he married Ann Frances Walden, who had emigrated from England as a passenger on that same voyage of the Dover Castle. From that point onwards he used the surname "Athfield", which appears to be a corruption of the English name Attfield, a name belonging to an apprentice seaman on the Czar. The Athfield name has become well known in New Zealand. I have not been able to find this name elsewhere.

So far I have been unable to locate him in Swedish records.

He advised he was born 10 June 1852 in Stockholm. Not clear as to whether this was Stockholm City or County. The State Archives of Sweden advised there are over 100 parishes in Stockholm County.

Anecdotal family information informs:
He was known by his nickname "Strong back Jack".
His father was a Brewer (of beer?)
His father remarried. John did not have a good relationship with his step-mother and ran away to sea (it is presumed this is when he crewed on the North Sea vessels).
He had a sister with a name similar to: Emma Carolina Lantina.

A listing has been found for the death, on 18 July 1875, of a female: Stromback, Emma Carolina Leontina, Mamsell, of 58 Hogsbergsg, St Maria Magdelena, Stockholm City. She died of tuberculosis at age 18. Is this his sister? So far I have been unable to find a birth record for this person.

Any assistance in finding John's origins would be greatly appreciated.