I believe it is the "Product Line Suffix". What that means is beyond me.
Intel® Xeon® Processor E3-1500M v5- and v6-based Mobile Workstations
The latest Intel® Xeon® processor numbering system is an alpha numeric representation of product line, product family, and version. Where applicable, an alpha suffix appears at the end of the processor name, which represents the processor line. The version number will not be used in the first processor generation.
Here is the link where I found this information:
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