There should be a number stamped on the underside of the shackle. May be hard to see but should be there. With that number it should be possible provide the combo.
That said, going off the 12 on the front of the shackle, the combo MIGHT be 5444. That would be right to stop, L-5, R-4, L-4, R-4. The shackle will not pop up - you need to pull up on it to open.
If that does not work and there are no numbers on the underside of the shackle I am out of ideas on how to help.
good luck!