Identify maker of Kings pattern silver plate serving fork

I have a fairly extensive collection of Kings silver plate flatware, mostly from Sheffield makers. I recently acquired a salad server fork whose maker I cannot identify. The fork is clearly stamped Sheffield England, but does not show the usual EPNS A1 imprint which is on most of my other flatware. Following the Sheffield imprint a series of four marks appears, ending with the number 58 enclosed within a shield. I am somewhat familiar with sterling hallmarks, since I have a number sterling hollowware pieces from my great grandparents, but I have no experience with silver plate marks. Can anyone decipher these marks? Any help would be greatly appreciated.

This is a new one on me. The letters are, I believe, J L E, but that doesn’t ring any bells in terms of manufacturer’s initials. As you say it is unusual not to have some sort of EP or plating quality indication.