Hi @Lorenzo Scalese ! Yes! It is in Location header, as @Tani Frankel mentioned. 

This is what I received in headers:

http://localhost:52773/fhir/r4/Patient//1983/_history/1
So, the id is 1983.

It is a bit different from what the public FHIR server on hl7.org/fhir returns - it returns the id also in a response.

Not sure though what is the "standard" behavior but if find it convenient enough to have the id in the response.