Jackson tune-o-matic bridge q

I believe it's large. I havn't seen small posts on anything other than USA made. If it's pencil eraser size it's the large post. If it's the size of a bic pen ink insert, then it's the small post. 99% sure you have large post. Another way to tell is if the post has a slot for a flat head screwdriver=large post. No slot for screwdriver=small post. Good luck.
 
you are correct sir, threads and all. Are you looking for a different bridge? If so I highly recommend the Tonepro's tuneOmatic bridge with the graphtech saddles! Their are locking studs that hold the bridge to your guitar so no more moving bridge when you change strings, can you say stabilized intonation.:rock: