iControl REST show content.

Following the documentation on page 29 of the REST user guide I am attempting to use the ?$stats=true to show content but can't seem to get it to work. I have tried with and without the backslash before the dollar as per the document. I think the syntax is correct, it certainly matches up with the example provided on p30.

xxxx@prometheus:~/vertica_traffic$ curl -k -u admin:xxxxxxx -H "Content-type: application/json" -X GET https://xxxxxxxx/mgmt/tm/ltm/pool/~qa~rmi_80_pool?\$stats=true | jq .

{ "code": 400, "message": "Query parameter $stats is invalid.", "errorStack": [] }

Pointers are gratefully received!