Is there a brand on the other shoulder? The 5 means fifth foal for that breeding year and the 4 is the last digit of the year of birth e.g. 2004 or 1994. Usually the breeders brand goes on the opposite shoulder.
We are trying to work his branding out after having a good look it seems to be a reverse k and a H or T with a wave underneath, unfortunately we have been unsuccessful in finding anything out about the brand