What do the 4 timing marks represent from left to right on a 1972 1600 cc dual port vw beetle?

That is something that is up in the air unless you are the original owner they could mean anything. You really need to buy the Bently manual to find out for sure. Pretty much all the pullys are interchangeable. My '75 Super has three and the Wifes '72 Super has two. The best thing to do would be to buy a degree wheel and if you want to keep the original pully then take the degree wheel off and put the old one back on after you time it. No guessing involved.