I believe what you are seeing is the primer Wisconsin used. .....Most of the TR series in the Bolens tube-frames had that primer under the brown.
The replacement engines from Wisconsin were painted gray or later, light green.
OK on the red. Reason I was suspicious was that fan shroud is the brown color and everything around it was red. Thought thy might have replaced the engine and used the original shroud.
Cannot read the serial number. Model is definitely 191-01. From the information I have that should be a magneto ignition. This one has a bttery ignition which was in the -02 run.