I am, by no means, an expert of grading. I am just a collector, even much younger than most regulars here I think.
Below are the photos of a weakly struck uncirculated 1920 half crown. It's not a high resolution picture but please note the surface and the crest.
The other two are a weakly struck 1915 Halfcrown, also in full lustre BUT British Extra-fine + condition due to possible bag marks on the high points of king's effigy, thus affecting the condition. It has a higher relief of king's effigy than post-1920 issues. Please note the crest and royal coat of arms as well. Grading is a very difficult business, and mostly not two people think similar or alike.
However, double eagle's piece is still a very lovely and worth to hold on piece. 1920-21 and 22 issues generaly come off very circulated, people didn't saved them, instead they stick to sterling silver 1911-1919 Halfcrowns.
The letter "P" in "Pense" on the motto of the Halfcrown is generally one of the highest points in a such coin. The wear on that letter tells us how long and much a coin is circulated. I learned than on this forum from one of the very oldschool (thanks sel_69) British coin collectors.
So, I still think double eagle's halfcrown is a British VG or maybe VG+ coin. Though, this is purely my opinion. Generally coins look better at hand than in scans.