You actually have a Trooper Mark III. This is an entirely different gun than the original Trooper model.
J124XX was made in 1970. The serial numbers that year went from J8601 to J50200.
The Trooper Mark III was part of a series of guns, all based on the Colt "J" frame.
Colt had two styles of grips for these, a target style, and the small "service" type grips that left the frame edges exposed.
The target style grips were made in two types.
The early to mid-production grips were a square butt design.
The later production grips were the same type grip only with the butt rounded off slightly.
The Trooper Mark III was only fitted with the two types of target grips, which had Gold Colt medallions.
Other guns in the "J" frame series were also occasionally fitted with target grips, but these "usually" had Silver medallions, and were "usually" made of a hardwood instead of the walnut used on the Trooper Mark III.
Early to mid-production Trooper Mark III Target grip.
Late production Trooper Mark III Target grip.