Hewlett Packard’s HP-45 was the first calculator to feature a Shift key. It was also, famously, a Reverse Polish Notation calculator, meaning that the numbers were entered first, followed by the operation to be performed (such as multiple or add). It rapidly became a beloved workhorse in the scientific and technical community and has been referenced by many subsequent designs. Wikipedia lists various present-day emulators which range from professional to artistic.
When released fifty years ago, Reverse Polish Notation calculators were not uncommon, but in the 21st century they appear unfamiliar and esoteric.
The calculator came with two manuals: The Owner’s Handbook and the Quick Reference Guide, both with blue covers displaying “HP-45” (or “HP·45”) in Premier Shaded and the title in Helvetica.
Printing on the calculator keys is Helvetica or something similar (except for the math italic x and y which appear to use different fonts for the printing on the key itself and on the adjacent fascia).
An aftermarket “Applications” guide was also available from Hewlett Packard (for $10!). Its cover features a magenta block with alternating black and white Helvetica set tight, stacked, and at an angle. The problem areas covered are mathematics, statistics, finance, engineering, and navigation, and they are set in Century Schoolbook (or similar).