Ohio Scientific Instrument Company (OSI), of Hiram, Ohio, made the "Challenger" series of microcomputers from 1975 to about 1977.

There were several different Challenger models, including the following:

Challenger II

Challenger II was a dual drive floppy disk system with 16K of RAM and came with DOS and BASIC on the diskettes. It sold for $1,964 fully assembled (December 1977).

Challenger IIP

Challenger IIP came with 4K RAM, full keyboard and audio cassette interface. It sold for $598 fully assembled (December 1977).

Challenger III

Challenger III was a 32K, triple processor machine compatible with 6502A, 6800 and Z-80 programs. It came with dual drive floppy disks and sold for $3,481 fully assembled (December 1977).

Challenger C3-B

The C3-B was offered in February 1978. It came with a 74 Mb Winchester disk drive, triple processor CPU (6502A, 6800, Z-80), Extended BASIC, 48K of RAM, OS-65U operating system. It was designed to be a powerful small business computer. The system, including a CRT, sold for $13,000.

Challenger 65-1K

Challenger 65-1K, fully assembled, 6502A microprocessor, serial interface, 1,024 words of memory. Cost was $439 (1976).

Challenger 65-4K

Challenger 65-4K, fully assembled, 6502A microprocessor, serial interface, $529.

Challenger 65V-4K

Challenger 65V-4K (includes OSI 440 video board), $675.

Challenger 68-1K

Challenger 68-1K, (6800 microprocessor), $459.

Challenger 68-4K

Challenger 68-4K, (includes OSI 4k BASIC on paper tape), $529.

Challenger floppy disk systems were extra, usually about $990 for a single drive, $1,490 for a dual drive (1976).

Some models connected to a television set for display.