Prompt Title: Inventarienummer as a property in a Wikibase

If you want to have an external "inventarienummer" as a property in a Wikibase, the most appropriate datatype to use would be "External identifier". This datatype is designed specifically for properties that refer to identifiers that are maintained outside of the Wikibase instance, such as inventar numbers, ISBNs, or DOIs.

When you create a property with the External identifier datatype, you can specify the format of the identifier, which can be helpful for validation and consistency. You can also specify the external authority that maintains the identifier, which can be useful for linking to external sources.

In summary, if you want to have an external "inventarienummer" property in your Wikibase, you should create a property with the External identifier datatype and specify the appropriate format and external authority for the identifier.