House flag, Stem jack from the Clan Line vessel 'Clan Sutherland' 1951. There should be plaid patterns but somehow I couldn't make it work...
This <a href="https://en.wikipedia.org/wiki/vector_image" class="extiw" title="w:vector image">vector image</a> includes elements  from this file:
Own work based on: <a rel="nofollow" class="external autonumber" href="https://www.rmg.co.uk/collections/objects/rmgc-object-572107">[1]</a>