Our first clue card ought to have provided you with the dragon, used here as the symbol for the Welsh football team. It seems that other few sports teams use the dragon, despite its fearsome reputation, and I can only find the Seattle Sea Dragons - but maybe you know of more? If so let us know.
The dragon has been used as the symbol for the Welsh football team. It has been that since 1920, but has undergone many changes, two even after this card was issued. If you want to see these, nip along to design site Dezeen/WFA where they are all pictured.
Strangely the emblem appears on cards way less than you would imagine. It appears that its first appearance is after the letters had been added, that is in the Pals Magazine "New Football Series" issued in 1923.
These cards are larger than normal, and on quite thin paper. However be aware that the set is of many sporting heroes, and only three are footballers, though there is a card of Welsh football referee, Clive Thomas.