I would wager it was restored by Delgrego, most likely in the '60s to '70s. The case colors and stock finish are trademark Delgrego.

I agree with Edgar and others- looks like older DelGrego work. Whatever it is it needs a good cleaning or I need new glasses.

I agree that DelGrego probably did the work. On the off chance that your father had the work done, you might contact DelGrego with your father's name. DelGrego files his work by surname of the customer. He may be able to locate the file for your gun.

Bill is correct. They have the records.
While some people may not like the colors of their case hardening, their work is very good. They know what they are doing.