Here we have an International match, on a card issued with German chocolate.
This is rather an oddity in the chocolate world as I have not been able to turn up any other cards in this series, though there are a couple of this one on various sites. In addition, the highest numbered Gartmann set listed on the Trading Card Database is Serie 629, issued in 1927 - but ours is over a hundred sets higher, at Serie 731. Whilst the Football Cartophilic Information Exchange raises the total a bit higher, to serie 700, but still does not include ours.
The subtitle, on the reverse, may give the clue to why this set is so scarce, for it says "Hamburg-Kopenhagen / Serie 731, Bild 6 / Tull Harder kopft" - and "Tull Harder kopft" also appears in the top right hand corner on the front of the card. Now Tull Harder was the nickname of Otto Fritz Harder, and the nickname was, indeed, after the English footballer, Walter Tull, the two men`s style of play being similar. Otto Harder was a really good footballer, who ought to have been remembered for that, and not the directions in which his political beliefs led him. Maybe this is why, after that war, and those events, this set was a bit tainted, and was allowed to slide away out of sight. Indeed, even in the 1970s, when he was included in a brochure, it was called in, and he was excised from the re-issue.
The "Hamburg-Kopenhagen" seems to suggest that the series shows matches in an early incarnation of the UEFA Cup, though I was surprised to learn that event only started in 1971.
The earliest attempt to match football teams from different regions seems to have been the British Home Championships, which was held from 1883, but only for England, Ireland, Scotland, and Wales.The first European version seems to have come along in 1927. That was the Central European International Cup, but neither Hamburg nor Copenhagen took part or would have been eligible, for it was country teams, and the only entrants were Austria, Czechoslovakia, Hungary, Italy, Switzerland and Yugoslavia - none of which could even have contained players from Hamburg and Copenhagen.
But maybe out there is someone who can either tell us more about an event it could be - or supply the names of some more cards from this series....?