In 1938, Colt introduced a .22 LR caliber conversion unit to
convert the Colt Government Model .45 and military
variations of the same gun to .22 LR. This unit utilized a
patented "floating chamber" to simulate the recoil of a .45
that was designed by David "Carbine" Williams. A big
selling point was that the shooter could use this unit for
target practice and the cost was approximately 1/7th that of
target practice with .45 caliber ammunition.
In 1939, the retail cost of this unit was
$34.00. The small walnut display case for the conversion
unit was available for an additional $3.50 and the large
walnut box for holding both the .22-.45 conversion unit and
wither the Government Model or National Match was $7.50.