Hewlett Packard, USA.
Hewlett Packard's first calculator was the 9100A electronic desktop model introduced in early 1968. It was a very advanced, scientific, programmable machine, taking magnetic cards and was priced at US$4,900.
Its HP-35, introduced in February 1972, was the first hand-held scientific calculator, and was the first in a series of highly specified hand-held calculators. These include the HP-80, the first hand-held calculator for business calculations, and the HP-65, the first programmable hand-held calculator.
also "The HP-35 Calculator The first electronic slide rule" in the "Collecting Calculators" section of this site, the book "A Guide to HP Handheld Calculators and Computers",
and the HP museum at www.hpmuseum.org.
Examples of Hewlett Packard calculators