The information on this once is scarce, but here is the link to the source of the photos I found.

Abridged/English cleaned up from the link:

The Equalizer converter was created in late 80s or early 90s. The creator, Philip Morgan was a warrant officer in the Rhodesian Selous Scouts, who emigrated to South Africa after the fall of Rhodesia. During his time in the Selous Scouts Phil Morgan acted as a gunsmith. According to some recollections colleagues said he had a hand in altering captured RPD machine guns.

The employees of the Reid-Daily the security company needed weapons like a compact carbine, but for self-loading weapons it was decided to abandon army automatic weapons for both legal and financial reasons.

Gunsmiths at the disposal of security personnel said multi-shot pistols equipped with removable devices could increase the accuracy and convenience of shooting.

Among other things, such conversion ones the sets would be completely "civilian" appearance, and armed the guard would not shock the public in public places with a weapon with the appearance of an "army machine gun."

Structurally, the converter is a welded rectangular pipe frame equipped with a front grip fitting to accommodate the flashlight on the front, and a shoulder stock on the rear.

The shoulder rest came in several versions both fixed and folding.

The Equalizer was compatible with pistols including CZ75/CZ85, Browning Hi-Power and derivatives, Beretta 92/92F, Z88, Star BM, BS both B and Colt Government in 9 mm, 38 Super and 45 ACP calibers.

The pistols used with Equalizer replace the grip panel with a specially made one metal with a deep hole at the bottom. The Equalizer frame secures through the hole with a spring loaded latch. Installing or removing the frame is said to take about 2 seconds.

Hilton Hamann, based on personal experience of ownership and operation of an Equalizer on a CZ75 pistol with approx. 3,000 rounds, gives Equalizer a positive review. For example, shooting from the hip complete darkness, without trying to use standard sights pistol devices, the author produced 10 in 1.97 seconds shots at a target located at a distance of 15 m, with a group of eight hits could be covered with a tea saucer, two bullets came a little lower, but both "over the body".

The device was tested with amateurs and "armed professionals", and results the shootings were comparable for all shooters, regardless experience.