I'm going to do a drive-by here. There are no Series '70 Commanders.

Original Series '70 pistols ran from 1970 to 1983. After 1969 Colt used the Accurizer barrel and collet bushing, (aka the Series '70 bushing) in Government and Gold Cup models. The Commander used a different bushing and never went to the Accurizer barrel/bushing. In 1983 Colt pistols became '80 Series pistols with the solid bushing, as always, and the firing pin safety.

Bill