Israel export hallmark.
The use of the Hebrew letter 'Mem'or מ
with a number in the center can be traced back to its use as a confirmation that the fees imposed, at the time, had been paid. Located within the letter Mem would be a number. The number that is found within the center of the letter was believed to represent the identification number of the tax collector, as it is likely that tax may have been imposed on the item if it were to be exported. Further research revealed that numbers repeatedly found on items originating from one source may indicate that an individual number was assigned to a specific gold or silversmith, jewelry maker, or retailer. No matter to which they were assigned these marks would still indicate that appropriate fees were been paid. Mem marks have been observed on items manufactured circa mid-20th century. Examples of numbers seen within the Mem letter have been; 8,16,25,30,31,32,83, but it is likely there are others. There has also been the occasional alphanumeric combination seen as well. It is to noted that the actual mark can look distinctly different from one example to the next. This would seem to indicate that the punches may have been create individually for each entity assigned a number. To date no list defining the numbers, their corresponding agent or region has been discovered.
Source; World Hallmarks Volume II ASia, Middle East, Africa with additional commentaries on non-hallmarking regions.