Asphalt shingle over metal roof?

Has anyone run across asphalt shingles installed over a previous metal roof. House is 121 yrs old. I haven’t been able to find any information on whether this is appropriate or not. Thanks

I don’t think it has ever been appropriate to install composition shingles on a metal roof other than the recommended plywood or OSB substrate sheathing as recommended by Manufacturers.

Any pictures?

No, i haven’t seen asphalt shingles installed on top of metal. I have seen metal installed over an old asphalt shingle roof several times. Not a conventional installation for shingles and not recommended.