LUSID allows you to define your own identification scheme(s) i.e. if you generate your own unique instrument identifiers to use across your organisation (as opposed to using 3rd party identifiers such as ISIN or OpenFIGI). LUSID can be configured to recognise your internally generated IDs across the LUSID platform so that you can reference these instruments using your own instrument identifiers.
Currently this configuration must be performed by email@example.com. Please get in touch if you would like to discuss setting this up.
You can list the available instrument identifiers with the GetInstrumentIdentifiers end point (https://docs.lusid.com/#operation/GetInstrumentIdentifiers).