When you get more information, you may want to check the IGI.

Go to: www.familysearch.com
Click: search
Enter First name: William and last name: Keig and select "isle of Man" from country, then press "enter"
On the right you will have a choice of data bases; choose: IGI/British Isles
When you get a list select "refine search" Choose "Birth/Christening" or "marriage" from Event.
You will get hundreds of William Keigs.

If you have the name of a parent or spouse or a date range, you can narrow your search to a manageable size.
If there is a message saying "Extracted birth or christening record...", it should be valid information.
Beware of all information which has a message starting: "Submitted by a member of the LDS church....." or where the date is "about 1860, etc.". These are not transcriptions from parish records and are very unreliable.
There were gunsmiths on the Isle, but I do not know how to help, without a name.