Beginning as an amateur shell enthusiast, she went on to work as a conchology curator for the Dominion Museum in Wellington.
She donated scientific and personal collections to the Museum of New Zealand Te Papa Tongarewa.
[1][2] She also donated specimens to the Auckland Museum, where her frequent correspondent, Baden Powell, was the chief conchologist.
[3][4] She was also the subject of a popular culture profile in the newspaper NZ Truth: How many women, once having survived the experience of being chased out of a pool by a large and indignant octopus, would go back and ask for more?
Few and far between such hardy ladies may be, but Miss Marjorie Mestayer, who has charge of the Conchological Department at the Dominion Museum, holds that such little incidents are part of the day’s work and that, anyhow, the octopus probably felt worse about it than she did…She was given her present post at the Museum several years back, mainly because Wellington could at that time produce no man who knew much more about shells than that they were curious things found on beaches.Mestayer died in 1955.