Real linoleum is the traditional material made from linseed oil, wood or cork flour and natural resins, pressed onto a strong woven jute backing. It’s solid, durable, slightly textured, and the jute backing looks like proper cloth so you can tell if it's the good quality stuff by looking at the underside where you can see the woven jute
Alongside it, manufacturers also produced cheaper lookalikes that weren’t true linoleum at all. These were made of mixed binders and fillers laid onto a felt or tar-paper backing — a stiff, papery material sometimes reinforced with bitumen. These imitations looked similar on the surface but were thinner, less robust, and far more prone to cracking.
The key difference is simple:
real linoleum = jute cloth backing;
cheaper imitations = tar paper / felt backing.
Real linoleum didn’t use asbestos — any asbestos concerns with old floors tend to come from the tar-paper/felt products or their adhesives, not from genuine jute-backed lino.