Chevrolet introduced the 1934 Standard series (DC) sedan in October 1934. This was very late in the model year. They advertised this car heavily. The postcard I have shown here was part of that advertising blitz. Look closely and you’ll see that this photo is actually a 1934 Master series (DA) sedan, that was retouched to show Standard features: (1) the headlights are shown as black (not chrome), but are Master in shape, (2) the rear quarter windows are shown as one piece (no wing windows), (3) not sure about the hubcaps, they are Master size but appear as painted, (4) the back is essentially flat. That means the spare tire was removed and also the integral trunk, if this was indeed a “sport sedan”. There may be other “tells”, but that’s what I see.
Special note to Bob Swanson: The term “Mercury” was used to describe the 1933 Standard series, but there is no record of Chevrolet themselves ever actually using it. True…you will find use of the term in many, many books and articles… but never in Chevrolet literature. I’ve seen it on boxes of aftermarket parts.