It's about function.Industrial antiques are the well worn stools, tables, office furniture, trash receptacles, lighting, equipment components and miscellaneous items from factories and schools, medical facilities, churches, farms and shops.
Their chief characteristic is that they were designed to do a job -- typically with little attention given to their appearance, and did it well, surviving various kinds of abuse in the process. For collectors, therein lies their charm. The aesthetic of highly authentic function over form.
Serious enthusiasts prefer that evidence of the function is in full flower, in the form of paint wear, rust, dents, etc., (but a seller who tries to pass off artificial wear is asking for an unhappy customer, as the look produced by years of use cannot be accurately replicated with clever painting techniques).
This appreciation for wear and tear shouldn't be interpreted to mean broken down or inoperable. To deserve the approval of industrial antique lovers, items need to perform the function for which they were designed.
It's the old story about one man's trash being another man's treasure. Not everybody "gets" industrial antiques, but for aficionados, rust is the new black and there's no chic like industrial chic.