The Brother Procal 408AY is a handheld calculator from 1973. It has a matt beige and brown plastic case with a painted metal keyboard surround. The calculator measures about 100mm x 155mm x 45mm and weighs 242g without batteries.
The 408AY features an 8 digit green vacuum fluorescent display (VFD), with a 9th digit used for negative numbers and overflow indicators. It is powered by 4 AA batteries or an optional AC adapter. With alkaline batteries, the 408AY can operate for around 12 hours.
The calculator has basic four function math capabilities, as well as percentages. There is a constant function that can be switched on and off. The plastic keys have a typewriter-like feel and layout.
Inside, the 408AY uses a NEC uPD273C processor and contains over 50 components including transistors, diodes, capacitors and resistors. The main circuit board connects to a smaller display board via 19 wires.
The 408AY has fairly robust logic for the time. The clear button can recover from overflows and other errors. There is no suppression of extra input digits, so entering too many digits generates an error. Negative numbers are shown with a minus sign on the 9th digit. Overall the calculator is described as “bug-free.”
The original manual is a 12 page booklet covering instructions in 4 languages. Helpful diagrams demonstrate the functions and capabilities. The manual provides examples for calculating percentages, discounts and markups.
In summary, the Brother 408AY is a well-built, full-size 1970s calculator with a vacuum fluorescent display. It has basic math functions and straightforward error recovery for a relatively “bug-free” user experience. The large typewriter-like keys and green display make the 408AY representative of vintage handheld calculators from the decade.