The installation is for HO-Scale Hobbytown RS3. It uses T1 decoder and was performed by Jean Lacroix.
The locomotive is complete with both a body and mechanism from former Hobbytown of Boston Company. The former Pitman motor was replaced by a Sagami that is smaller and more easy to insulate from the metal body of the locomotive.
First, you will have to locate and remove all the screws underneath the locomotive that holds the body. Normally you have 2 screws under the cab and 2 others at the opposite end near the steps at rear and front. Remove the shell of the locomotive which is spitted in two by the cab. Remove all lamps hooked to the motor or otherwise connected. If they are of 1,5volts you should discard them and save them for future projects.
In this locomotive, the motor was a Pitman open frame type and is not insulated from the frame or the body. You will probably have to put aside the motor and change it for a smaller size one, like Sagami or the like. On this unit, you should install extra contacts using phosphor bronze wires inserted in plastic tubing on each truck in order to have better electrical pick up current from the track. This is done on the side of the locomotive that has the wheels insulated. Look at the installation on the GP7 to see a picture of that.
You will need to unsolder the wires that were hooked to the motor. You will then solder the black wire from the harness to one of the truck and the red wire to the other truck. After this is done, you have to solder the grey harness wire on one of the motor contact and the orange on the other. You can put a tape over the motor contacts to prevent a short circuit with the metal body.
Then, it is a good idea to take care of the lights. I used Leds to replace the original 1.5v bulbs. Solder the wires as mentioned in the instructions that came with your T1. The lights were then simply glued behind the holes for the headlights. All the wires soldered together should be covered with electrical shrink tubing or electrical tape.