Here's an explanation of "steel toy maker", in case you haven't come across it before.
In the 18th and 19th centuries the manufacture of “toys” was a major industry in Birmingham. But these “toys” had nothing to do with children’s games. The term “Birmingham toys” refers to a multitude of small, decorative personal accessories. Their production provided work for thousands, gained major export markets and led to the development of manufacturing techniques which could be applied in other fields. Birmingham’s first directory, Sketchley’s Directory of 1767, lists 100 firms in the “toy” and related trades and describes the industry as follows:
.….for the information of Strangers we shall here observe, that these Articles are divided into several Branches, as the Gold and Silver Toy Makers, who make Trinkets, Seals, Tweezer and Tooth Pick cases, Smelling Bottles, Snuff Boxes, and Filigree Work, such as Toilets, Tea Chests, Inkstands, etc. etc. The Tortoise Toy maker, makes a beautiful variety of the above and other Articles; as does also the Steel, who makes Cork Screws, Buckles, Draw and other Boxes, Snuffers, Watch Chains, Stay Hooks, Sugar Knippers, etc., and almost all these are likewise made in various Metals, and for Cheapness, Beauty and Elegance no Place in the world can vie with them.
I don't think it's implausible that a locksmith might turn his hand to making steel "toys".
I don't need to tell you of the problems researching a name as common as Jones, but I would say David is one of the less common forenames to be found in Victorian Birmingham. With Jones, his origins could be Welsh.
I take it that it's Samuel's baptism that you have found?
You say you have his marriage certificate, but can't find his marriage - can you clarify that, please.
ETA I'm confused now - I'm sure your opening post said
"marriage cert has his father David a steel toy maker".
