Modular vs Manufactured how to tell difference

[Tom T.]

Question for you seasoned vets and contractors.

What are the visual clues to differentiate between the two.
Here is what I believe, please add to the list or correct me.

Manufactured: or (Double Wide) I believe these could be used interchangeably. Always has a metal frame underneath. I beams and a setup where wheels and axles would go.

Normally has no attic access.  Normally has a low pitch roof.
Should have the metal tags on the outside or information on an interior closet or pantry.

Modular: Always has a wooden underside. Like a normal stick built home and can be on a crawlspace or a slab.

In this case, I am being told something is modular (by HUD) but from what I see it is Manufactured. I have been asked to prove why I say it is manufactured. There are no plates or information on it that I can see. This unit was built in 1989.

Opinions, Comments.  Thanks!