For comparison, here's a pic of me and Colleen Bak at the grave in 2017. (I'm 5'9".)
This 1927 "unveiling" of the grave monument can cause some confusion. Houdini himself had erected and unveiled the full exedra in 1916. But a year after his death, the bust and, I believe, the mosaic were added by the S.A.M. An official dedication ceremony attended by 500 people took place on Oct. 30, 1927, which is likely when the Bess photo was taken. Below is a full account from the New York Times.