Yep. German K.98k serial numbers (with a few exceptions) consisted of a four digit number and one of two suffix letters. They ran 1-9999, 1a-9999a, 1b-9999b, and so on, for each maker and each year. When 9999z was reached, they went to 1aa-9999aa, 1ab-9999ab, etc.
So a full identification of a K.98k (and other German mililtary weapons) must include the maker (or maker's code), the year, and the complete serial number including the suffix letter(s), e.g., "German K.98k, dot code, 1944, Serial #8988ab."