Perfect idea.
I always had the idea of going to Canada and converting my money (back when the rate was $1 US to $1.57 CND) to all quarters and then coming back to the US (since the US accepts Canadian quarters as the same as US) and switching em out for $$$.
That way for every US dollar of quarters I’d get a return of 50 cents. It was flawless (theoretically if I did it in low enough amounts mixed with US to not get converted over), but now the rates what $1 US - $1.10 CND?