These are the tools of the trade a 72 year old industry dinosaur uses to underwrite group medical plans, projecting future costs, rate setting, reserve requirements, quantifying IBNR, etc.
Cost projections have historically proven to be accurate within a 4% margin of actual outcomes.
The pen was purchased at Walmart or some other similar place. The calculator is over 20 years old and still reliable. The work sheet memorializes the exercise.