What's the correct shape of the plexiglass for a 1961 Seamaster?

Hi, I have a 1961 Seamaster with case number 147 65 sc-61 and according to various online sources, the correct plexiglass for this watch is PZ5072. However, I'm not sure if the original version is round or box-shaped ( I believe the original version was round )? Was it replaced with a box-shaped version? If so I would have to try to find NOS.