This cannot really be classified as a calculator, since it's just a reference table of the Periodic Elements. Granted, many MTs may not need to refer to this, but medical transcription can cover such a wide range of medical information that it certainly is not hard to imagine that some MTs will find this reference worthwhile. This is especially true if the MT is performing transcription for a physician or other medical practitioner who submits or does reports for various medical journals or papers. If you are an MT who was in high school 20-30 years ago, you may not even recognize many of the elements, as new ones have been discovered over the years.
The Periodic Table of Elements