At the beginning, Miss Marple arrives in town with one suitcase. And the end she is leaving with two.
According to the gravestone Miss Pinkerton died in 1955, but the MG being driven by Bridget Conway had the number 2326EL which was issued in 1959.
At around the 60 minutes mark there is an inquest scene. The coroner is smartly dressed as one would expect in the 1950s. At a glance his shoes look correct as well but the soles are the problem; molded patterned soles that would only be seen on boots at that time. It would be the 1970s or later than adult men's shoes would be constructed with such soles.