Wash your mouth out!!!!!! Never, ever, refer to an RRS Officer's 'beret' as a Tam!!!
Other ranks wear the Tam O'shanter. Officers wear the Balmoral. Very subtle but definite differences.
Balmoral is a subtly different lighter colour, has a slightly smaller and more ellipse shape crown... and has a different (silk) lining.
The badge is attached in the same way as on the Glengarry, but over the RRS tartan patch instead of the silk cockade. The hackle is attached to the Balmoral (or Tam) in the same way as the blackcock on the Glengarry.
Edited to add pic. Jonny in the Balmoral, the other chap in the Tam O'Shanter. You can see the different colour and slight difference in shape clearly here.
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