Although A.J. Croker entered a maker's mark at the London Assay Office for use on articles of gold and silver he may not have been an actual worker in precious metals except, perhaps, in a very small way. Culme suggests as much by describing him as a violin chin rest maker. This means that either Croker made his own mounts, which to judge from this present example would have been fairly easy for a competent craftsman working in various materials, or he ordered his mounts from another workshop.
It is well to remember that the appearance of his so-called maker's mark on pieces infers no more than he took responsibility that the silver (or gold) struck with that mark to be submitted to the Assay Office was of the correct fineness.
For what it's worth, it does seem likely in this case that Croker was the actual maker of this piece, including the mount, because he was clearly in a small way of business. At the time he was living there in the 1890s Bermondsey was a somewhat depressed part of London and he may have been working from home, perhaps in part of a multi-occupancy house or even a garden shed.
It would be interesting to know how Croker marketed the objects he made. Did he, for instance, supply a single retailer or a number of them; and which retailers might they have been? Given his stated trade and that he made batons as well, the answer might very well be found in trade papers connected with the musical instrument business rather than those for goldsmiths, silversmiths and jewellers.