REST API Search SR's

Ok the API documentation is really bad for this.

Lets say I have an SR with a key of this:

        {
            "key": "CustomColumn52sr",
            "value": "d12f7702-2c0a-4f2e-b5c1-33100d2183f2",
            "valueClass": "",
            "mandatory": false,
            "editable": true,
            "type": "text",
            "defaultValue": null,
            "customColumnType": "string",
            "valueCaption": "d12f7702-2c0a-4f2e-b5c1-33100d2183f2",
            "keyCaption": "~Transaction ID"
        },

I need to be able to search for the value d12f7702-2c0a-4f2e-b5c1-33100d2183f2. I have tried to put a search string together but I can’t figure it out.

Anyone have done this before?

Thanks!