I need a consensus of opinion please.

I am attempting to identify a Jack Qualtrough who is listed in the Nevada US 1880 census as bn IOM, aged 37 thus yob

My experience has it that Jack is usually a nickname for John, but that it can sometimes be used for James

I have viewed the original document online and the age is definitely 37, so there is no error in transcription.

The IGI has no John or James Qualtrough bn in 1843, and the nearest John listed was bp 1841 with the next two in 1846 & 1848. The only James was bp 1848. I realise that the IGI is not an exhaustive listing....and also the fact that Jack may not have been baptised close to birth and thus could still be one of the above with exception of John 1841,

Any suggestions for how I could further find a way of identifying Jack Qualtrough would be most welcome

Thank you

Elizabeth