In https://developers.arcgis.com/rest/services-reference/enterprise/rest-api-versioning.htm
The version parameterWhile the request parameters and JSON responses are compatible with previous versions, for certain output formats (f=lyr), clients can explicitly specify the version of the requests they are issuing and the response that they want. They can specify this with a version parameter v.
https://<mapserviceResource>?f=lyr&v=10.0&v=9.3
In the above request, the client has explicitly indicated that the request it is issuing, as well as the response it is expecting, should be 10.0 compatible.
What is the meaning of &v=9.3 ?
