Many thanks Thomas for explaining about the return (and non-return) of insignia. I learn something new every day.

Interesting observation 992234177. While I had noticed the different shapes previously, I had not appreciated the significance. I wonder if in some cases it was a question of individual preference? I recollect reading somewhere that Louis Mountbatten had his jewelled Garter star set somewhat differently and hoped that, because it was an expensive setting, the slight differences would be accepted. I don't recollect whether this was permitted or not.

Was Queen Elizabeth the Queen Mother wearing her Garter star in an unusual position for the 1948 service?

https://www.britishpathe.com/video/mountbatten-honoured-at-garter-service