The hallmark is London and you are correct with 1983. Unfortunately there are no published references for London marks of this period so the only way you will be able to find the name of AJS will be to contact the London Assay Office directly. Contact details are on their web site at https://www.assayofficelondon.co.uk/contact.
If you do manage to get a name we would appreciate it if you could update this topic with the details - or it is possible that one of our other contributors may have come across this mark before...