These two photos are of a dog spying a flask during Prohibition. These were taken at the Potomac River and are dated to February 23, 1922. The dog was actually trained to find hidden stores of liquor. (An early sniffer dog).
The dog looks a lot like a golden retriever, even though I’m a bit skeptical that it was one. There were almost none of them in the US at the time.
Retrieving dogs are a commonly used as sniffer dogs. All they have to do is associate the scent of what they are retrieving with the substance in question and then build upon that.