You should contact the vendor. If they do not have any code, perhaps they will have a data sheet or at least a schematic.
Can you see any codes/part numbers on the sides of the digits? Or the transistors?
I should warn you, it looks like it was designed by someone who is not very expert. There are no bypass caps for the chips, for example, and no reservoir caps. These could be added, if you can solder reasonably well.