Sorry for my late arrival to the thread, but... Injection tooling needs to be cared for on a regular basis, or it will deteriorate quite quickly. As a general rule, it'll come n two parts. The first part is the carrier. That's the part that will allow the injection to connect between the mould, and the machine proper. The second part is the imprint/impression side. This side sits within the carrier and the mould, and takes the shape of the injected material. (in this case, plastic).
Most injection businesses will regard the carrier as the more important part in day-to-day operations. It will normally keep the common machine location features, across a wide set of dimensions across the industry. They won't be scale specific, but will conform to things like ISO sizes, limits & fits. It's quite normal to see a toolroom strip out a tool, re-use the carrier, and store the imprint tool. That's normally where the trouble starts. Natural degradation sets in, as the lesser used tools get quietly forgotten. After all, they're running a business....
Ownership of tools will depend on usage as well. You will sometimes see tools made with just a few imprints, the stripped out components will be stored. You can't use them, as responsibility/ownership will rest with the owner. You'll know it's there, but to all intents & purposes it might has well gone down with the Titanic.
Cheers,
Ian.