[maj1]

I have a 509 block with block number 3951509. How do I tell if it is a 2bt or 4bt seeing how they were both made under that number. It has 4 bolts but it has had alot of machine work. not sure if cap are aftermarked or not. Outter bolt are bolted at an angle. I have seen splayed cap but am not sure if they are an older style.